Laminated film

ABSTRACT

A laminated film includes a polarizing plate, a retardation film, and a first pressure-sensitive adhesive layer provided in this order, wherein the polarizing plate includes a polarizer, a first protective layer placed on a side of the polarizer where the retardation film is provided, and a second protective layer placed on another side of the polarizer which is opposite to the side where the retardation film is provided, the retardation film is a stretched film comprising a norbornene resin,
         the first pressure-sensitive adhesive layer includes a pressure-sensitive adhesive that may be produced by crosslinking a composition comprising a (meth)acrylate (co)polymer and a crosslinking agent comprising a peroxide as a main component. The laminated film has both good adhesion to a liquid crystal cell and easy peelability, and may improve the uniformity in a screen of liquid crystal display.

TECHNICAL FIELD

The invention relates to laminated film having a polarizing plate, aretardation film, and a pressure-sensitive adhesive layer.

BACKGROUND ART

Liquid crystal displays are attracting attention because of theirfeatures such as slimness, lightweight and low power consumption andwidely used in portable equipment such as cellular phones and watches,office automation equipment such as personal computer monitors andnotebook computers, domestic electrical equipment such as video camerasand liquid crystal televisions, and so on. Laminated films includinglaminate of retardation films and any of various polarizing plates areused in conventional Liquid crystal displays.

For example, a patent document 1 listed below discloses that a liquidcrystal display which has a polarizing plate and a retardation filmhaving a refractive index ellipsoid satisfying the relation nx>nz>nyplaced on one side of an in-plane switching (IPS) liquid crystal cell,has improved contrast ratio in oblique directions.

However, liquid crystal displays produced with a conventional laminatedfilm cause a problem. For example, leakage of light or significantchanges in color (also referred to as a large amount of color shift)occur depending on the viewing direction, when a black image displayedon a screen is viewed from oblique directions, or optical unevenness isobtained, when backlight is allowed to run for certain hours.

Such a laminated film is generally bonded to a liquid crystal cell withan interposed pressure-sensitive adhesive layer. However, a conventionallaminated film causes a problem in which the laminated film is difficultto separate from a liquid crystal cell, or a certain component of thelaminated film (such as a retardation film or a pressure-sensitiveadhesive layer) is left on the surface of a liquid crystal cell afterthe process of peeling the laminated film. In general, liquid crystaldisplay undergo inspection before they are shipped. As a result of theinspection, if the laminated film itself is defective or if there isforeign matter between the laminated film and the liquid crystal cell,the laminated film will be separated such that the liquid crystal cellcan be recycled (or reworked). Ideally, the laminated film should bebonded to the liquid crystal cell such that peeling or bubbles can beprevented even in a high-temperature, high-humidity environment, whilethe laminated film should be easily separable from the liquid crystalcell such that the liquid crystal cell can be recycled without causingdamage or a change in cell gap. In conventional technologies, it hasbeen difficult to satisfy such conflicting features at the same time.Thus, there have been demands for liquid crystal display panels in whichsuch problems are overcome.

Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No.11-305217

The invention has been made in order to solve the problems, and it is anobject of the invention to provide a laminated film which may improvethe display uniformity in liquid crystal display, and a laminated filmwhich may have both good adhesion to a liquid crystal cell and easypeelability.

As a result of investigations for solving the problems, the inventorshave found that the objects can be achieved with the laminated filmdescribed below, and have completed the invention.

In an aspect of the invention, a laminated film includes: a polarizingplate; a retardation film; and a first pressure-sensitive adhesivelayer, provided in this order. The polarizing plate includes: apolarizer; a first protective layer placed on a side of the polarizerwhere the retardation film is provided; and a second protective layerplaced on another side of the polarizer which is opposite to the sidewhere the retardation film is provided. The retardation film is astretched film which includes a norbornene resin. The firstpressure-sensitive adhesive layer includes a pressure-sensitive adhesivethat may be produced by crosslinking a composition which includes a(meth)acrylate (co)polymer and a crosslinking agent comprising aperoxide as a main component.

In a preferred embodiment of the invention, the first protective layerand/or the second protective layer is a polymer film comprising acellulose resin.

In a preferred embodiment of the invention, the first protective layeris substantially optically isotropic.

In a preferred embodiment of the invention, the first protective layerhas a refractive index ellipsoid satisfying the relation nx≈nz>ny,wherein nx is a refractive index in a slow axis direction, ny is arefractive index in a fast axis direction, and nz is a refractive indexin a thickness direction;

In a preferred embodiment of the invention, the retardation film has arefractive index ellipsoid satisfying the relation nx>nz>ny, wherein nxis a refractive index in a slow axis direction, ny is a refractive indexin a fast axis direction, and nz is a refractive index in a thicknessdirection;

In a preferred embodiment of the invention, the retardation film has anin-plane retardation (Re[590]) of 80 nm to 350 nm that is measured at23° C. and a light wavelength of 590 nm.

In a preferred embodiment of the invention, the retardation film has anNz coefficient of 0.1 to 0.7, wherein the Nz coefficient is calculatedfrom the formula: Rth[590]/Re[590], wherein Re[590] is an in-planeretardation measured at 23° C. and a light wavelength of 590 nm, andRth[590] is a retardation in a thickness direction that is measured at23° C. and a light wavelength of 590 nm.

In a preferred embodiment of the invention, the retardation film has anabsolute value of photoelastic coefficient of 1×10⁻¹² to 10×10⁻¹² thatis measured at 23° C. and a light wavelength of 590 nm.

In a preferred embodiment of the invention, the first pressure-sensitiveadhesive layer has an adhesive force (F_(A)) of 2 N/25 mm to 10 N/25 mmat 23° C. to a glass plate, wherein the adhesive force is measured by aprocess that includes pressing a laminated film with a width of 25 mmagainst a glass plate by one reciprocation of a 2 kg roller to bond thelaminated film to the glass plate, aging the laminate at 23° C. for onehour, and then measuring an adhesive strength when the laminated film ispeeled in a 90-degree direction at a rate of 300 mm/minute, wherein theadhesive strength is determined as the adhesive force.

In a preferred embodiment of the invention, the first pressure-sensitiveadhesive layer has an anchoring force (F_(B)) of 10 N/25 mm to 40 N/25mm at 23° C. to the retardation film, wherein the anchoring force ismeasured by a process that includes pressing a laminate of thepressure-sensitive adhesive layer and the retardation film each with awidth of 25 mm against the surface of an indium tin oxidevapor-deposited onto a polyethylene terephthalate film by onereciprocation of a 2 kg roller to bond the laminate to the polyethyleneterephthalate film, aging the laminate at 23° C. for one hour, and thenmeasuring an adhesive strength when the polyethylene terephthalate filmis peeled together with the pressure-sensitive adhesive layer in a180-degree direction at a rate of 300 mm/minute, wherein the adhesivestrength is determined as the anchoring force.

In a preferred embodiment of the invention, there is a difference(F_(B)−F_(A)) of 5 N/25 mm or more between the anchoring force (F_(B))of the pressure-sensitive adhesive layer at 23° C. to the retardationfilm and the adhesive force (F_(A)) of the pressure-sensitive adhesivelayer at 23° C. to a glass plate. The anchoring force is measured by aprocess that includes pressing a laminate of the pressure-sensitiveadhesive layer and the retardation film each with a width of 25 mmagainst the surface of an indium tin oxide vapor-deposited onto apolyethylene terephthalate film by one reciprocation of a 2 kg roller tobond the laminate to the polyethylene terephthalate film, aging thelaminate at 23° C. for one hour, and then measuring an adhesive strengthwhen the polyethylene terephthalate film is peeled together with thepressure-sensitive adhesive layer in a 180-degree direction at a rate of300 mm/minute. The adhesive strength is determined as the anchoringforce, and the adhesive force is measured by a process that includespressing a laminated film with a width of 25 mm against a glass plate byone reciprocation of a 2 kg roller to bond the laminate to the glassplate, aging the laminate at 23° C. for one hour, and then measuring anadhesive strength when the laminated film is peeled in a 90-degreedirection at a rate of 300 mm/minute, wherein the adhesive strength isdetermined as the adhesive force.

In a preferred embodiment of the invention, the (meth)acrylate(co)polymer is a copolymer of a (meth)acrylate monomer having a straightor branched alkyl group of 1 to 8 carbon atoms and another(meth)acrylate monomer having a straight or branched alkyl group of 1 to8 carbon atoms in which at least one hydrogen atom is replaced with ahydroxyl group.

In a preferred embodiment of the invention, the crosslinking agentincluding the peroxide as a main component has a content of 0.01 to 1.0part by weight, base on 100 parts by weight of the (meth)acrylate(co)polymer.

In a preferred embodiment of the invention, the first pressure-sensitiveadhesive layer includes: a pressure-sensitive adhesive that may beproduced by crosslinking a composition comprising a (meth)acrylate(co)polymer; and an isocyanate group-containing compound, a silanecoupling agent, wherein a crosslinking agent comprising a peroxide as amain component, the isocyanate group-containing compound has a contentof 0.005 to 1.0 part by weight, based on 100 parts by weight of the(meth)acrylate (co)polymer, and the silane coupling agent has a contentof 0.001 to 2.0 parts by weight, based on 100 parts by weight of the(meth)acrylate (co)polymer.

In a preferred embodiment of the invention, the pressure-sensitiveadhesive has a glass transition temperature (Tg) of −70° C. to −10° C.

In a preferred embodiment of the invention, the pressure-sensitiveadhesive has a moisture content of 1.0% or less.

In a preferred embodiment of the invention, the laminated film furtherincludes a second pressure-sensitive adhesive layer between thepolarizing plate and the retardation film, wherein the secondpressure-sensitive adhesive layer includes a pressure-sensitive adhesivethat may be produced by crosslinking a composition comprising a(meth)acrylate (co) polymer, a silane coupling agent, and a crosslinkingagent comprising an isocyanate group-containing compound as a maincomponent.

A liquid crystal display panel including the laminated film describedabove and liquid crystal cell is provided in one aspect of theinvention.

A liquid crystal display is provided in another aspect of the invention.The liquid display includes the liquid crystal display panel describedabove.

EFFECTS OF THE INVENTION

The laminated film of the invention, has a stretched film comprising anorbornene resin as a retardation film and thus can form a liquidcrystal display that can resist distortion-induced optical unevennessand provide a high level of display uniformity. When the retardationfilm has a refractive index ellipsoid satisfying the relation nx≧nz>ny,amounts of leakage of light in oblique directions and amount of colorshift in the liquid crystal display are significantly smaller than thosein conventional liquid crystal displays. The laminated film of theinvention also uses a pressure-sensitive adhesive that may be producedby crosslinking a specific composition, and thus the pressure-sensitiveadhesive can be strongly bonded to the retardation film. In such aliquid crystal display, peeling from a substrate of the liquid crystalcell (glass substrate) or bubbles can be prevented even in ahigh-temperature, high-humidity environment can provide a practicallysufficient level of adhesive force and adhesion time. On the other hand,when the laminated film is peeled off and the liquid crystal cell isrecycled, neither pressure-sensitive adhesive layer nor retardation filmis left on the surface of the liquid crystal cell, and each optical filmcan be separated and removed by a small force. Thus, the productivity ofthe liquid crystal display can be significantly increased with no changein the cell gap of the liquid crystal cell or no damage to thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a laminated film accordingto a preferred embodiment of the invention.

FIG. 2 is a schematic diagram showing the concept of a typical processfor manufacturing a polarizer for use in the invention.

FIG. 3 is a schematic diagram showing the concept of a typical processfor manufacturing a retardation film for use in the invention.

FIG. 4 is a schematic diagram showing the concept of a typical processfor manufacturing a first pressure-sensitive adhesive layer for use inthe invention.

FIG. 5 is a schematic cross-sectional view of a laminated film accordingto an embodiment of the invention.

FIG. 6 is a schematic cross-sectional view of a liquid crystal displaypanel according to a preferred embodiment of the invention.

FIG. 7 is a schematic cross-sectional view of a liquid crystal displayaccording to a preferred embodiment of the invention.

FIG. 8 is a graph showing the relationship between the in-planeretardation (Re[590]) and the Nz coefficient of each of the retardationfilms obtained in Reference Examples 1 to 12.

FIG. 9 is a graph showing the relationship between the in-planeretardation (Re[590]) and the thickness direction retardation (Rth[590])of each of the retardation films obtained in Reference Examples 1 to 12.

FIG. 10 is a graph showing Y values at a polar angle of 600 alongazimuth angles of 0° to 360° with respect to the liquid crystal displaysof Example 3 and Comparative Example 3.

FIG. 11 is a graph showing Δa*b* values at a polar angle of 60° alongazimuth angles of 0° to 360° with respect to the liquid crystal displaysof Example 3 and Comparative Example 3.

FIG. 12 is a photograph of the surface of a glass plate after theprocess of peeling the laminated film of Example 4.

FIG. 13 is a photograph of the surface of a glass plate after theprocess of peeling the laminated film of Comparative Example 4.

DESCRIPTION OF REFERENCE MARKS

In the drawings, reference numeral 10 represents a laminated film. 20 apolarizing plate, 21 a polarizing plate, 22 a first protective layer, 23a second protective layer, 30 a retardation film, 41 a firstpressure-sensitive adhesive layer, 42 a second pressure-sensitiveadhesive layer, 50 a liquid crystal cell, 51 and 51′ substrates, 52 aliquid crystal layer, 100 a liquid crystal display panel, 80 a backlightunit, 81 a backlight, 82 a reflecting film, 83 a diffusing plate, 84 aprism sheet, 85 a brightness enhancement film, 200 a liquid crystaldisplay, 300 a feeding part, 310 an aqueous iodine solution bath, 320 anaqueous solution bath containing boric acid and potassium iodide, 330 anaqueous potassium iodide-containing solution bath, 340 drying means, 350a polarizer, 360 a winding part, 401, 403 and 405 feeding parts, 414,416 and 419 winding parts, 404 and 406 shrinkable films, 407 and 408laminating rolls, 409 heating means, 501 and 506 feeding parts, 503 acoater, 504 temperature control means, 507 and 508 laminating rolls, and510 a winding part.

BEST MODE FOR CARRYING OUT THE INVENTION

A. Outline of the Laminated Film

FIG. 1 is a schematic cross-sectional view of a laminated film accordingto a preferred embodiment of the invention. It should be noted that thelength, width and thickness of each component in FIG. 1 are not shown ina true ratio for convenience of easy reference. This laminated film 10includes at least a polarizing plate 20, a retardation film 30, and afirst pressure-sensitive adhesive layer 41, provided in this order. Thepolarizing plate 20 includes a polarizer 21, a first protective layer 22placed on a side of the polarizer 21 where the retardation film 30 isprovided, and a second protective layer 23 placed on another side of thepolarizer 21 which is opposite to the side where the retardation film 30is provided. The retardation film 30 is a stretched film which includesa norbornene resin. The first pressure-sensitive adhesive layer 41includes a pressure-sensitive adhesive that may be produced bycrosslinking a composition which includes a (meth)acrylate (co)polymerand a crosslinking agent comprising a peroxide as a main component. Whenused in liquid crystal displays, such a laminated film can resistdistortion-induced optical unevenness and provide a high level ofdisplay uniformity. Even in a high-temperature, high-humidityenvironment, such a laminated film does not cause peeling or bubbles andcan provide a practically sufficient level of adhesive force andadhesion time. On the other hand, such a laminated film is characterizedby having a high level of easy peelability (also referred to asreworkability) when separated from a liquid crystal cell.

In an embodiment of the invention, any adhesive layers (not shown) canbe provided between the polarizer 21 and the first protective layer 22,between the polarizer 21 and the second protective layer 23. As usedherein, the term “adhesive layer” is intended to include any layercapable of bonding the surfaces of adjacent optical components at apractically sufficient level of adhesive strength and adhesion time. Forexample, the adhesive layer may be a layer of an adhesive agent, apressure-sensitive adhesive layer, an anchor coating layer, or the like.The adhesive layer may be a multilayer structure including an anchorcoating layer formed on the surface of the adherend and an adhesive orpressure-sensitive adhesive layer formed thereon. The adhesive layer mayalso be a subvisible thin layer (also called hair line).

In practical, a release liner (not shown) may be provided on a side ofthe first pressure-sensitive adhesive layer 41 which is opposite to theside where the retardation film 30 is provided. A surface protectivefilm may also be provided on a side of the second protective layer 23which is opposite to the side where the polarizer 21 is provided. Therelease liner and the surface protective film are used in order toprevent the laminated film from being soiled or scratched during amanufacturing process or handling of the laminated film. The releaseliner and the surface protective film, thus be peeled off before thelaminated film is practically used.

The laminated film preferably has a thickness of 100 μm to 600 μm, morepreferably of 200 μm to 400 μm. Setting the thickness of the firstprotective layer in the above range allows a production of a polarizingplate with a high level of mechanical strength.

It will be understood that the laminated film of the invention is notlimited to the embodiments described above, and, for example, any otheroptical component may be placed between the respective components shownin FIG. 1. The thickness of the laminated film also includes thethickness of the components above and the other components such assurface treatment layer formed on the second protective layer.

B. Polarizing Plate

Referring to FIG. 1, the polarizing plate 20 for use in the inventionincludes a polarizer 21, a first protective layer 22 placed on a side ofthe polarizer where the retardation film is provided, and a secondprotective layer 23 placed on another side of the polarizer which isopposite to the side where the retardation film is provided. In anembodiment of the invention, the first protective layer 22 and thesecond protective layer 23 may be the same or different.

The first polarizing plate 20 preferably includes adhesive layers (notshown) that are provided between the polarizer 21 and the firstprotective layer 22 and between the polarizer 21 and the secondprotective layer 23, respectively, to bond the respective protectivelayers to the polarizer. The polarizer sandwiched between the protectivelayers as described above can form a polarizing plate with a high levelof mechanical strength. In addition, the polarizer can be prevented fromexpanding or shrinking even in a high-temperature, high-humidityenvironment, so that the resulting polarizing plate can have a highlevel of optical properties.

The polarizing plate preferably has a thickness of 45 μm to 250 μm, morepreferably of 70 μm to 220 μm. The polarizing plate with a thickness inthe above range can have a high level of mechanical strength.

The transmittance (also referred to as single-piece transmittance) ofthe polarizing plate is preferably 40% or more, more preferably 42% ormore, when measured at 23° C. and a light wavelength of 550 nm. Thesingle-piece transmittance has a theoretical upper limit of 50% and apossible upper limit of 46%.

The polarizing plate preferably has a degree of polarization of 99.8% ormore, more preferably of 99.9% or more. The degree of polarization has atheoretical upper limit of 100%. If the single-piece transmittance andthe degree of polarization are each set in the above range, liquidcrystal displays with low level of light leakage in the normal direction(with a high level of contrast ratio, as a result) can be obtained.

According to the National Bureau of Standards (NBS), the hue value a(single-piece a value) of the polarizing plate is preferably −2.0 ormore, more preferably −1.8 or more. The value a is ideally zero.According to the National Bureau of Standards (NBS), the hue value b(single-piece b value) of the polarizing plate is preferably 4.2 orless, more preferably 4.0 or less. The value b is ideally zero. If thevalues a and b of the polarizing plate is close to zero, liquid crystaldisplays capable of displaying images in bright colors can be obtained.

The single-piece transmittance, the degree of polarization and the huemay be measured using a spectrophotometer (DOT-3 (product name)manufactured by Murakami Color Research Laboratory Co., Ltd.).Specifically, the degree of polarization may be determined by ameasurement method that includes measuring the parallel transmittance(H₀) and crossed transmittance (H₉₀) of the polarizing plate andcalculating the degree of polarization from the formula: degree ofpolarization (%)={(H₀−H₉₀)/(H₀+H₉₀)}^(1/2)×100. The paralleltransmittance (H₀) is the transmittance value of a parallel laminatedpolarizing plate that is produced by laminating two pieces of the samepolarizing plate in such a manner that their absorption axes areparallel to each other. The crossed transmittance (H₉₀) is thetransmittance value of a cross laminated polarizing plate that isproduced by laminating two pieces of the same polarizing plate in such amanner that their absorption axes are orthogonal to each other. Thesetransmittances above are Y values which have undergone luminositycorrection in the two-degree visual field (C illuminant) according toJIS Z 8701 (1982).

B-1. Polarizer

Any appropriate polarizer capable of converting natural light orpolarized light into linearly polarized light may be used as thepolarizer described above. The polarizer is preferably an iodine- ordichroic dye-containing stretched film mainly composed of a polyvinylalcohol resin. As used herein, the term “stretched film” refers to apolymer film that is produced by applying a tension to an unstretchedfilm at an appropriate temperature in such a manner that the orientationof the molecules is increased along the tensile direction.

The polarizer may have any appropriate thickness, which is chosendepending on the purpose. The polarizer preferably has a thickness of 5μm to 50 μm, more preferably of 10 μm to 30 μm.

The polyvinyl alcohol resin may be produced by polymerizing a vinylester monomer and saponifying the resulting vinyl ester polymer.Examples of the vinyl ester monomer include vinyl formate, vinylacetate, vinyl propionate, vinyl valerate, vinyl laurate, vinylstearate, vinyl benzoate, vinyl pivalate, and vinyl versatate.

The polyvinyl alcohol resin preferably has a degree of saponification of95.0% by mole to 99.9% by mole. The degree of saponification may bedetermined according to JIS K 6726 (1994). A polarizer with a high levelof durability can be obtained using a polyvinyl alcohol resin with adegree of saponification in the above range.

The polyvinyl alcohol resin may have any appropriate average degree ofpolymerization, which is chosen depending on the purpose. The averagedegree of polymerization is preferably from 1200 to 3600. The averagedegree of polymerization may be determined according to JIS K 6726(1994).

Any appropriate forming method may be used to produce a polymer filmmainly composed of the polyvinyl alcohol resin. For example, such aforming method is described in Example 1 of JP-A No. 2000-315144.

The polymer film mainly composed of the polyvinyl alcohol resinpreferably contains a polyhydric alcohol as a plasticizer. Thepolyhydric alcohol may be used to further increase the stretchabilityand dyeability of the polarizer. Examples of the polyhydric alcoholinclude ethylene glycol, glycerin, propylene glycol, diethylene glycol,triethylene glycol, tetraethylene glycol, and trimethylolpropane. One ormore of these polyhydric alcohols may be used singly or in anycombination. The content of the polyhydric alcohol is preferably morethan 0 and not more than 30 parts by weight, based on 100 parts byweight of the total solids of the polyvinyl alcohol resin.

The polymer film mainly composed of the polyvinyl alcohol resin mayfurther contain a surfactant. The surfactant may be used to furtherincrease the stretchability and dyeability of the polarizer. Thesurfactant is preferably a nonionic surfactant. Examples of the nonionicsurfactant include lauric acid diethanolamide, coconut oil fatty aciddiethanolamide, coconut oil fatty acid monoethanolamide, lauric acidmonoisopropanolamide, and oleic acid monoisopropanolamide. The contentof the surfactant is preferably more than 0 and not more than 5 parts byweight, based on 100 parts by weight of the polyvinyl alcohol resin.

Any appropriate dichroic substance may be used as the dichroic dye. Asused herein, the term “dichroic” refers to optical anisotropy in whichtwo directions including an optical axis direction and another directionperpendicular thereto differ in light absorption. Examples of thedichroic dye include Red BR, Red LR, Red R, Pink LB, Rubin BL, BordeauxGS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG,Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R,Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, BrilliantViolet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct SkyBlue, Direct Fast Orange S, and Fast Black.

The polymer film mainly composed of the polyvinyl alcohol resin for usein the invention may be a commercially available film itself. Examplesof such a commercially available polymer film mainly composed of apolyvinyl alcohol resin are Kuraray Vinylon Film (trade name)manufactured by Kuraray Co., Ltd., Tohcello Vinylon Film (trade name)manufactured by Tohcello Co., Ltd. and Nichigo Vinylon Film (trade name)manufactured by Nippon Synthetic Chemical Industry Co., Ltd.

A typical method for producing the polarizer is described with referenceto FIG. 4. FIG. 4 is a schematic diagram illustrating the concept of atypical process for producing the polarizer for use in the invention.For example, a polymer film 301 mainly composed of a polyvinyl alcoholresin is subjected to a swelling process and a dyeing process, while itis fed from a feeder 300 and immersed in an aqueous iodine solution bath310 and undergoes a tension in the machine direction of the film betweenrolls 311 and 312 in different circumferential velocities. The film isthen subjected to a crosslinking process, while it is immersed in anaqueous solution bath 320 containing boric acid and potassium iodide andundergoes a tension in the machine direction of the film between rolls321 and 322 in different circumferential velocities. The crosslinkedfilm is immersed in an aqueous solution bath 330 containing potassiumiodide and subjected to washing with water by means of rolls 331 and332. The film washed with water is dried by drying means 340 so that itsmoisture content is typically adjusted to 10% to 30% and wound on awinding part 360. Through these processes, the polymer film mainlycomposed of the polyvinyl alcohol resin is stretched to 5 to 7 times itsoriginal length and results in a polarizer 350.

B-2. First Protective Layer

Referring to FIG. 1, the first protective layer 22 is placed between thepolarizer 21 and the retardation film 30. The first protective layer isused in combination with the second protective layer in order to preventthe polarizer from contracting or expanding and from being deterioratedby ultraviolet rays.

The first protective layer may have any appropriate thickness, which ischosen depending on the purpose. The protective layer preferably has athickness of 10 μm to 100 μm, more preferably of 20 μm to 100 μm.Setting the thickness of the first protective layer in the above rangeallows a production of a polarizing plate with a high level ofmechanical strength and durability.

The first protective layer preferably has a transmittance of 90% ormore, when measured at a light wavelength of 590 nm and 23° C. Thetransmittance has a theoretical upper limit of 100% and a possible upperlimit of 96%.

The absolute value of the photoelastic coefficient (C[590] (m²/N)) ofthe first protective layer is preferably from 1×10⁻¹² to 100×10⁻¹², morepreferably from 1×10⁻¹² to 60×10⁻¹². In the above range of the absolutevalue of the photoelastic coefficient, a polarizing plate that resistsdistortion-induced optical unevenness can be obtained.

The first protective layer used in the liquid crystal display panel ofthe invention is placed between the polarizer and the liquid crystalcell, and in some cases, therefore, the optical properties of the firstprotective layer has an effect on the display characteristics of theliquid crystal display. Thus, the first protective layer to be usedpreferably has an appropriate retardation value.

In a preferred embodiment of the invention, the first protective layeris substantially optically isotropic. Herein, the case where it issubstantially optically isotropic is intended to include the case wherethe in-plane retardation (Re[590]) is less than 10 nm and the absolutevalue of the retardation in the thickness direction (|Rth[590]|) is lessthan 10 nm.

As used herein, Re[590] represents an in-plane retardation measured at alight wavelength of 590 nm and 23° C. When the measurement object is asimple film, the term “in-plane retardation,” as used herein, meansretardation in the plane of the film, and when the measurement object isa laminate, the term “in-plane retardation,” as used herein, meansretardation in the plane of the whole of the laminate. Re[590] may becalculated from the formula: Re[590]=(nx−ny)d, wherein nx and nyrepresent refractive indices in the slow axis direction and in the fastaxis direction, respectively, at a wavelength of 590 nm, and d (nm)represents the thickness of the measurement object. The slow axiscorresponds to a direction in which the in-plane refractive index ismaximum.

When the first protective layer is substantially optically isotropic,the Re[590] of the first protective layer should be less than 10 nm,preferably 8 nm or less, more preferably 5 nm or less. In the aboverange of Re[590], a liquid crystal display with very low level of colorshift and light leakage in oblique directions can be obtained, when thefirst protective layer is used in combination with a retardation filmhaving the optical properties described later.

As used herein, Rth[590] represents retardation in the thicknessdirection that is measured at a light wavelength of 590 nm and 23° C.When the measurement object is a simple film, the term “retardation inthe thickness direction,” as used herein, means a retardation in thedirection of the thickness of the film, and when the measurement objectis a laminate, the term “retardation in the thickness direction,” asused herein, means a retardation in the direction of the thickness ofthe whole of the laminate. Rth[590] may be calculated from the formula:Rth[590]=(nx−nz)d, wherein nx and nz represent refractive indices in theslow axis direction and in the thickness direction, respectively, at awavelength of 590 nm, and d (nm) represents the thickness of themeasurement object. The slow axis corresponds to a direction in whichthe in-plane refractive index is maximum.

When the first protective layer is substantially optically isotropic,the absolute value (|Rth[590]|) of the Rth[590] of the first protectivelayer should be less than 10 nm, preferably 8 nm or less, morepreferably 5 nm or less. In the above range of |Rth[590]|, a liquidcrystal display with very low level of color shift and light leakage inoblique directions can be obtained, when the first protective layer isused in combination with a retardation film having the opticalproperties described later.

Re[590] and Rth[590] may be measured using KOBRA21-ADH (trade name)manufactured by Oji Scientific Instruments. From the formulae (i), (ii)and (iii) below, nx, ny and nz may be obtained by computer calculationusing the in-plane retardation (Re) at 23° C. and a wavelength of 590nm, a retardation (R40) measured with the slow axis inclined by 40degrees, the thickness (d) of the measurement object, and the averagerefractive index (n0) of the measurement object, and then Rth may becalculated from the formula (iv) below.Re=(nx−ny)d  (i)R40=(nx−ny′)d/cos(φ)  (ii)(nx+ny+nz)/3=n0  (iii)Rth=(nx−nz)d  (iv)wherein φ and ny′ are expressed by the formulae (v) and (vi) below,respectively.φ=sin⁻¹[sin(40°)/n0]  (v)ny′=nynz[ny ² sin²(φ)+nz ² cos²(φ)]^(1/2)  (vi)

In another embodiment of the invention, the refractive index ellipsoidof the first protective layer has the relation nx≈ny>nz, wherein nx is arefractive index in its slow axis direction, ny is a refractive index inits fast axis direction, and nz is a refractive index in its thicknessdirection. The protective layer whose refractive index ellipsoid has therelation nx≈ny>nz ideally has an optical axis in the normal direction.Herein, nx≈ny means not only that nx is completely equal to ny but alsothat nx is substantially equal to ny. Herein, the case where nx issubstantially equal to ny is intended to include the case where thein-plane retardation (Re[590]) is less than 10 nm.

When the relation of the refractive index ellipsoid nx≈ny>nz isexpressed using Re[590] and Rth[590], the first protective layersatisfies the formula (1): Re[590]<10 nm and the formula (2) 10nm≦Rth[590], wherein Re[590] is the in-plane retardation at 23° C. and awavelength of 590 nm, and Rth[590] is the retardation in the thicknessdirection at 23° C. and a wavelength of 590 nm.

When the refractive index ellipsoid of the first protective layer hasthe relation nx≈ny>nz, the Re[590] of the first protective layer shouldbe less than 10 nm, preferably 8 nm or less, more preferably 5 nm orless. In the above range of Re[590], a liquid crystal display with verylow level of color shift and light leakage in oblique directions can beobtained, when the first protective layer is used in combination with aretardation film having the optical properties described later.

When the refractive index ellipsoid of the first protective layer hasthe relation nx≈ny>nz, the Rth[590] of the first protective layer shouldbe 10 nm or more, preferably from 20 nm to 100 nm, more preferably from30 nm to 80 nm. In the above range of Rth[590], a liquid crystal displaywith very low level of color shift and light leakage in obliquedirections can be obtained, when the first protective layer is used incombination with a retardation film having the optical propertiesdescribed later.

Any appropriate material may be used to form the first protective layer.Preferably, the first protective layer is formed of a polymer filmcontaining a cellulose resin. Cellulose resins have good adhesion to thepolarizer and thus can form a polarizing plate with each componentprevented from peeling even in a high-temperature, high-humidityenvironment.

Any appropriate cellulose resin may be used as the cellulose resindescribed above. The cellulose resin is preferably an organic acid esteror mixed organic acid ester of cellulose in which the hydroxyl groups ofthe cellulose are partially or entirely replaced with an acetyl group, apropionyl group and/or a butyl group. Examples of the organic acid esterof cellulose include cellulose acetate, cellulose propionate andcellulose butyrate. Examples of the mixed organic acid ester ofcellulose include cellulose acetate propionate and cellulose acetatebutyrate. For example, the cellulose resin may be obtained by the methoddescribed in Paragraphs [0040] to [0041] of JP-A No. 2001-188128.

A commercially available product may be used as the cellulose resinwithout modification. Alternatively, a commercially available resin maybe subjected to any appropriate polymer modification and then used.Examples of the polymer modification include copolymerization,crosslinking and modification of molecular end, stereoregularity or thelike. Examples of commercially available cellulose resins includecellulose acetate propionate resins manufactured by Daicel FinechemLtd., cellulose acetate manufactured by Eastman Chemical Company,cellulose butyrate manufactured by Eastman Chemical Company, andcellulose acetate propionate manufactured by Eastman Chemical Company.

The cellulose resin preferably has a weight average molecular weight(Mw) of 20,000 to 1,000,000, more preferably of 25,000 to 800,000, whenmeasured by a gel permeation chromatography (GPC) method usingtetrahydrofuran as a solvent. Specifically, the above weight averagemolecular weights are values measured by the method described in thesection of EXAMPLES. In the above range of weight average molecularweight, the resulting product can have a high level of mechanicalstrength, solubility, formability, and casting workability.

The cellulose resin preferably has a glass transition temperature (Tg)of 110° C. to 185° C. If the Tg is 110° C. or higher, films with goodthermal stability can be easily obtained. If the Tg is 185° C. or lower,good formability can be obtained. The glass transition temperature (Tg)may be determined by DSC method according to JIS K 7121.

Any appropriate forming method may be used to produce the celluloseresin-containing polymer film. Examples of forming methods includecompression molding, transfer molding, injection molding, extrusionmolding, blow molding, powder molding, FRP molding, and solvent casting.The forming method is preferably a solvent casting method, because itcan form a polymer film with a high level of smoothness and opticaluniformity.

Specifically, the solvent casting method may include deaerating a thicksolution (a dope) prepared by dissolving, in a solvent, a resincomposition containing a resin as a main component, an additive and soon, uniformly casting the thick solution into a sheet on the surface ofan endless stainless steel belt or a rotating drum, and vaporizing thesolvent to form a film. Appropriate conditions may be chosen for thefilm forming process, depending on the purpose.

The cellulose resin-containing polymer film may further contain anyappropriate additive. Examples of such an additive include aplasticizer, a heat stabilizer, a light stabilizer, a lubricant, anantioxidant, an ultraviolet absorbing agent, a flame retardant, acolorant, an antistatic agent, a compatibilizing agent, a crosslinkingagent, and a thickener. The content of the additive is preferably morethan 0 and not more than 20 parts by weight, based on 100 parts byweight of the cellulose resin.

A commercially available film may be used as the first protective layerwithout modification. Alternatively, a commercially available film maybe subjected to a secondary process such as stretching and/or shrinkingand then used. Examples of the commercially available celluloseresin-containing polymer film include FUJITAC series manufactured byFuji Photo Film Co., Ltd. (such as FUJITAC ZRF80S, TD80UF and TDY-80UL(trade names)) and KC8UX2M (trade name) manufactured by Konica MinoltaOpto, Inc.

B-3. Second Protective Layer

Referring to FIG. 1, the second protective layer 23 is placed on oneside of the polarizer 21, which was opposite to the side where the firstprotective layer 22 is provided. The second protective layer is used incombination with the first protective layer in order to prevent thepolarizer from contracting or expanding and from being deteriorated byultraviolet rays.

Any appropriate layer may be used as the second protective layer. Alayer having a thickness, a transmittance and a photoelastic coefficienteach in the range described in the section C-1 is preferably used as thesecond protective layer.

Any appropriate material may be used to form the second protectivelayer. Preferably, the second protective layer is formed of a polymerfilm containing a cellulose resin. Examples of the celluloseresin-containing polymer film that may be used are preferably the sameas described in the section C-2.

When used in the liquid crystal display panel of the invention, thesecond protective layer is placed outside the liquid crystal cell (onthe viewer or backlight side). For example, the second protective layermay be placed so as to form the outermost surface on the viewer side inthe first polarizing plate, or the second protective layer may be placedon an upper artificially-roughened part of a prism sheet in the secondpolarizing plate. Preferably, therefore, the second protective layerfurther includes a surface treatment layer on the outside (opposite tothe side where the polarizer is provided).

Any appropriate treatment may be used to form the surface treatmentlayer, depending on the purpose. For example, the surface treatmentlayer may be formed by hard-coat treatment, antistatic treatment,anti-reflective treatment (also referred to as anti-reflectiontreatment), diffusing treatment (also referred to as antiglaretreatment), or any other treatment. These surface treatment layers maybe used to prevent the screen from being soiled or scratched or toprevent the displayed image from being made difficult to see by thereflection of room fluorescent light or sunlight on the screen. Thesurface treatment layer to be used is generally formed by bonding atreatment agent to the surface of a base film. The base film may alsoserve as the second protective layer. The surface treatment layer mayalso be a multilayer structure such as a laminate of an antistatictreatment layer and a hard coat treatment layer formed thereon.

A commercially available polymer film having a surface treatment layermay be used as the second protective layer without modification.Alternatively, a commercially available polymer film may be subjected toany surface treatment and then used. Examples of the commerciallyavailable polymer film with a diffusing treatment (antiglare treatment)layer include AG150, AGS1, AGS2, and AGT1 manufactured by Nitto DenkoCorporation. Examples of the commercially available polymer film with ananti-reflective treatment (ant-reflection treatment) layer include ARSand ARC manufactured by Nitto Denko Corporation. Examples of thecommercially available film with a hard coat treatment layer and anantistatic treatment layer include KC8UX-HA (trade name) manufactured byKonica Minolta Opto, Inc. Examples of the commercially available polymerfilm with an anti-reflection surface treatment layer include ReaLookseries manufactured by NOF Corporation.

B-4. Adhesive Layers

In the polarizing plate, any appropriate adhesive, pressure-sensitiveadhesive and/or anchor coating agent may be used for the adhesive layersthat are provided to bond the first and second protective layers to thepolarizer, respectively.

The adhesive layers may each have any appropriate thickness, which ischosen depending on the purpose. Preferably, the adhesive layers eachhave a thickness of 0.01 μm to 50 μm. If the adhesive layers each have athickness in the above range, the bonded polarizer and protective layercan be free from peeling or separation so that practically sufficientstrength and time of adhesion can be achieved.

A water-soluble adhesive mainly composed of a polyvinyl alcohol resin ispreferably used as a material for forming the adhesive layer, because ithas good adhesion to the polarizer and the protective layer and ishighly workable, productive and economical. A commercially availablewater-soluble adhesive mainly composed of a polyvinyl alcohol resin maybe used as it is for the adhesive layer or may be mixed with a solventor an additive before use. Examples of the commercially availablewater-soluble adhesive mainly composed of a polyvinyl alcohol resininclude Gosenol series manufactured by Nippon Synthetic ChemicalIndustry Co., Ltd. (such as Gosenol NH-18S, GH-18S and T-330 (tradenames)) and Gosefimer series manufactured by Nippon Synthetic ChemicalIndustry Co., Ltd. (such as Gosefimer Z-100, Z-200 and Z-210 (tradenames)).

A composition may be obtained by adding a crosslinking agent to thewater-soluble adhesive and subjected to crosslinking to form theadhesive layer. Any appropriate crosslinking agent may be used as theabove crosslinking agent. Examples of the crosslinking agent includeamine compounds, aldehyde compounds, methylol compounds, epoxycompounds, isocyanate compounds, and multivalent metal salts. Acommercially available product may be used as the crosslinking agentwithout modification. Examples of such a commercially availablecrosslinking agent include an amine compound manufactured by MitsubishiGas Chemical Company, Inc. (Methaxylenediamine (trade name)), analdehyde compound manufactured by Nippon Synthetic Chemical IndustryCo., Ltd. (Glyoxal (trade name)) and a methylol compound manufactured byDainippon Ink and Chemicals, Incorporated (Watersol (trade name)).

C. Retardation Film

The retardation film for use in the invention is a norborneneresin-containing stretched film. The absolute value of the photoelasticcoefficient of the norbornene resin is smaller than that of otherresins. Therefore, the norbornene resin can form a retardation film thatresists optical unevenness and fluctuations in the retardation valueeven when strains are caused by the expansion or contraction of thepolarizer, so that a liquid crystal display panel and a liquid crystaldisplay each with a high level of display uniformity can be obtained.

The refractive index ellipsoid of the retardation film preferably hasthe relationship nx>nz>ny. When the retardation film having such arelationship is placed on one or both sides of a liquid crystal cell ina liquid crystal display, light leakage and color shift in obliquedirections can be significantly reduced. In general, a liquid crystaldisplay in which two polarizing plates are placed on both sides of aliquid crystal cell such that the directions of their absorption axesare orthogonal to each other may cause light leakage in obliquedirections. Specifically, when the long side of such a liquid crystalpanel is defined as being in a direction of 0°, the amount of leakage oflight tends to be maximum in oblique directions of 45° and 135°. Whenthe retardation film having the above relationship of the refractiveindex ellipsoid is used in the laminated film of the invention, therecan be provided liquid crystal displays in which light leakage issignificantly reduced in oblique directions as compared withconventional liquid crystal displays.

When the relation of the refractive index ellipsoid nx>nz>ny isexpressed using Re[590] and Rth[590], the retardation film satisfies theformula below.10 nm≦Rth[590]<Re[590]  (3)wherein Re[590] is the in-plane retardation measured at a lightwavelength of 590 nm and 23° C., and Rth[590] is the retardation in thethickness direction measured at a light wavelength of 590 nm and 23° C.

Conventionally, no retardation film having the refractive indexellipsoid relation nx>nz>ny has been obtained yet using norborneneresin-containing stretched films. This is because it is more difficultto produce a retardation by stretching in norbornene resin-containingpolymer films than in other resins and because norborneneresin-containing polymer films themselves are too brittle to bestretched. In addition, in order to make the refractive index (nz) inthe film thickness direction larger than one (ny) of the in-planerefractive indices, relatively large stress has to be applied to films,which has been made the production of retardation films more difficult.According to the invention, retardation films having the relationnx>nz>ny are actually obtained using norbornene resin-containingstretched films by the production method using a specific shrinkablefilm as described later.

Referring to FIG. 1, the retardation film 30 is placed between the firstpressure-sensitive adhesive layer 41 and the first protective layer 22placed on one side of the polarizing plate 21. Preferably, the directionof the slow axis of the retardation film 30 is substantially parallel,substantially orthogonal, or substantially 45° to the direction of theabsorption axis of the polarizer 21. More preferably, the direction ofthe slow axis of the retardation film 30 is substantially orthogonal tothe direction of the absorption axis of the polarizer 21. Using theretardation film in the specific positional relation allows theproduction of a liquid crystal display in which light leakage and colorshift are further reduced in oblique directions. As used herein, theterm “substantially parallel” is intended to include the case where theangle between the direction of the slow axis of the retardation film 30and the direction of the absorption axis of the polarizer 21 is 0°±2.0°,preferably 0°±1.0°, more preferably 0°±0.5°. As used herein, the term“substantially orthogonal” is intended to include the case where theangle between the direction of the slow axis of the retardation film 30and the direction of the absorption axis of the polarizer 21 is90°±2.0°, preferably 90°±1.0°, more preferably 90°±0.5°. As used herein,the term “substantially 45°” is intended to include the case where theangle between the direction of the slow axis of the retardation film 30and the direction of the absorption axis of the polarizer is 45°±2.0°,preferably 45°±1.0°, more preferably 45°±0.5°. If the deviation from theideal angle between the direction of the slow axis of the retardationfilm and the direction of the absorption axis of the polarizing plate(the deviation from 0°, 90°, or 45°) is smaller, a liquid crystaldisplay with a higher contrast ratio in the normal and obliquedirections can be obtained.

The retardation film may have any appropriate thickness, which is chosendepending on the purpose. Preferably, the retardation film has athickness of 20 μm to 200 μm. If the thickness of the retardation filmis set in the above range, a desired retardation value can be obtained,and the resulting retardation film can have a high level of mechanicalstrength and durability.

The retardation film preferably has a transmittance of 90% or more, whenmeasured at a light wavelength of 590 nm and 23° C. The transmittancehas a theoretical upper limit of 100% and a possible upper limit of 96%.

The absolute value of the photoelastic coefficient (C[590] (m²/N)) ofthe retardation film is preferably from 1×10⁻¹² to 10×10⁻¹², morepreferably from 1×10⁻¹² to 8×10⁻¹², particularly preferably from 1×10⁻¹²to 6×10⁻¹². In the above range of the absolute value of the photoelasticcoefficient, a retardation film that resists distortion-induced opticalunevenness can be obtained.

One or both sides of the retardation film for use in the invention maybe subjected to surface modification treatment. The surface modificationtreatment may be performed by any appropriate method. For example, thesurface modification treatment may be a dry process or a wet process.Examples of the dry process include discharge treatment such as coronatreatment and glow discharge treatment, flame treatment, ozonetreatment, UV-ozone treatment, ultraviolet treatment, and ionizingradiation treatment such as electron beam treatment. Surfacemodification treatment (dry process) suitable for the retardation filmis preferably corona treatment. As used herein, the term “coronatreatment” refers to a process that includes modifying the surface of afilm by allowing the film to pass through a corona discharge fieldgenerated by applying high frequency/high voltage between a groundeddielectric roll and an insulated electrode and thus causing dielectricbreakdown and ionization of the air between the electrodes.

Examples of the wet process include alkali treatment and anchor coatingtreatment. As used herein, the term “alkali treatment” refers to aprocess that includes modifying the surface of a film by immersing thefilm in an alkali treatment solution which is a solution of a basicsubstance in water or an organic solvent. The term “anchor coatingtreatment” refers to a process that includes previously applying ananchor coating agent to the surface of a laminated film in order toincrease the adhesion between the film and the pressure-sensitiveadhesive layer. Surface modification treatment (wet process) suitablefor the retardation film is preferably anchor coating treatment. Theanchor coating agent preferably includes a polymer containing an aminogroup in its molecule, particularly preferably includespolyethyleneimine.

C-1. Materials for Forming Retardation Film

Any appropriate norbornene resin may be used for the retardation film.Such a norbornene resin preferably has a high level of transparency,mechanical strength, thermal stability, and moisture blocking propertiesand preferably resists distortion-induced optical unevenness.

As used herein, the term “norbornene resin” refers to a (co)polymer or(co)polymers that are produced using a norbornene monomer having anorbornene ring as part or all of the starting material(s) (a monomer ormonomers). As used herein, the term “(co)polymer” means a homopolymer ora copolymer.

The norbornene resin may be produced using, as a starting material, anorbornene monomer having a norbornene ring (in which a double bond isformed in a norbornane ring). The norbornene resin in a state of(co)polymer may have or may not have a norbornane ring in itsconstitutional unit(s). For example, the norbornene resin having anorbornane ring-containing constitutional unit in a state of (co)polymermay be produced using tetracyclo[4.4.1^(2,5).1^(7,10).0]deca-3-ene,8-methyltetracyclo[4.4.1^(2,5).1^(7,10).0]deca-3-ene,8-methoxycarbonyltetracyclo[4.4.1^(2,5).17,10.0]deca-3-ene, or the like.For example, the norbornene resin having no norbornane ring in itsconstitutional unit in a state of (co)polymer may be produced using amonomer capable of forming a five-membered ring by cleavage. Examples ofthe monomer capable of forming a five-membered ring by cleavage includenorbornene, dicyclopentadiene, 5-phenylnorbornene, and derivativesthereof. When the norbornene resin is a copolymer, it may be a randomcopolymer, a block copolymer or a graft copolymer, while its moleculemay have any structural arrangement.

A commercially available product may be used as the norbornene resinwithout modification. Alternatively, a commercially available norborneneresin may be subjected to any appropriate polymer-modification beforeuse. Examples of commercially available norbornene resins include ARTONseries manufactured by JSR Corporation (such as ARTON FLZR50, ARTONFLZR70, ARTON FLZL100, ARTON F5023, ARTON FX4726, ARTON FX4727, ARTOND4531, and ARTON D4532 (trade names)), ZEONOR series manufactured byNippon Zeon Co., Ltd. (such as ZEONOR750R, ZEONOR1020R, and ZEONOR 1600(trade names)), APL series manufactured by Mitsui Chemicals, Inc. (suchas APL8008T, APL6509T, APL6011T, APL6013T, APL6015T, and APL5014T (tradenames)), and COC resin (TOPAS (trade name)) manufactured by TICONA.

Examples of the norbornene resin include (A) a resin of a hydrogenatedring-opening (co)polymer of a norbornene monomer and (B) a resin of anaddition (co)polymer of a norbornene monomer. The ring-opening copolymerof the norbornene monomer is intended to include a resin of ahydrogenated ring-opening copolymer of one or more norbornene monomers,and an α-olefin, a cycloalkene and/or a non-conjugated diene. The resinof the addition copolymer of the norbornene monomer is intended toinclude a resin of an addition copolymer of one or more norbornenemonomers, and an α-olefin, a cycloalkene and/or a non-conjugated diene.The norbornene resin is preferably (A) a resin of a hydrogenatedring-opening (co)polymer of a norbornene monomer, because such a resinhas good formability and can be formed into a retardation film with ahigh retardation value by stretching at low draw ratios.

The resin of the hydrogenated ring-opening (co)polymer of the norbornenemonomer may be prepared by a process including the steps of subjectingthe norbornene monomer or the like to a metathesis reaction to form aring-opening (co)polymer and then hydrogenating the ring-opening(co)polymer. Examples of such a process include the method described in“Development and Application Techniques of Optical Polymer Materials,”published by NTS INC., 2003, pp. 103-111, and the methods described inParagraphs [0059] to [0060] of JP-A No. 11-116780, Paragraphs [0035] to[0037] of JP-A No. 2001-350017, and Paragraph [0053] of JP-A No.2005-008698. The resin of the addition (co)polymer of the norbornenemonomer may be prepared by the method described in Example 1 of JP-A No.61-292601.

The weight average molecular weight (Mw) of the norbornene resin ispreferably from 20,000 to 500,000, more preferably from 30,000 to200,000, in terms of the value measured by gel permeation chromatography(GPC) with a solvent of tetrahydrofuran. The weight average molecularweight may be measured by the method described in the section ofEXAMPLES. If the norbornene resin has a weight average molecular weightin the above range, products with a high level of mechanical strength,solubility, formability, or casting operability can be produced.

The norbornene resin preferably has a glass transition temperature (Tg)of 110° C. to 185° C., more preferably of 120° C. to 170° C.,particularly preferably of 125° C. to 150° C. A Tg of 110° C. or higherallows easy production of films with good thermal stability, and a Tg of185° C. or lower allows easy control of the in-plane retardation and thethickness direction retardation by stretching. The glass transitiontemperature (Tg) may be determined by DSC method according to JIS K7121.

Any appropriate forming method may be used to produce a polymer filmcontaining the norbornene resin. Examples of such a forming methodinclude those described in Section C-2. The forming method is preferablya solvent casting method, because polymer films with a high level ofsmoothness and optical uniformity can be obtained by such a method.

The polymer film containing the norbornene resin may also contain anyappropriate additive. Examples of the additive include a plasticizer, aheat stabilizer, a light stabilizer, a lubricant, an antioxidant, anultraviolet absorbing agent, a flame retardant, a colorant, anantistatic agent, a compatibilizing agent, a crosslinking agent, and athickener. The content of the additive is preferably more than 0 and notmore than 10 parts by weight, based on 100 parts by weight of thenorbornene resin.

The polymer film containing the norbornene resin may be obtained from aresin composition containing the norbornene resin and another resin. Anyappropriate resin may be selected as the other resin. A styrene resin ispreferred as the other resin. The styrene resin may be used to controlthe wave dispersion or photoelastic coefficient of the retardation film.The content of the other resin is preferably more than 0 and not morethan 30 parts by weight, based on 100 parts by weight of the norborneneresin.

A commercially available polymer film containing the norbornene resinmay be used as it is. Alternatively, a commercially available film maybe subjected to a secondary process such as stretching and/or shrinkingand then used. Examples of the commercially available polymer filmcontaining the norbornene resin include ARTON series manufactured by JSRCorporation (such as ARTON F, ARTON FX and ARTON D (trade names)) andZEONOR series manufactured by Optes Inc. (such as ZEONOR ZF14 and ZEONORZF16 (trade names)).

C-2. Optical Properties of Retardation Film

The Re[590] of the retardation film may be any appropriate value, whichis chosen depending on the purpose. The Re[590] of the retardation filmmay be 10 nm or more, preferably from 80 nm to 350 nm, more preferablyfrom 120 nm to 350 nm, still more preferably from 160 nm to 280 nm.Setting Re[590] in the above range allows the production of liquidcrystal displays with very low level of color shift and light leakage inoblique directions.

An appropriate value may be chosen as the Re[590] of the retardationfilm, depending on the Rth[590] of the first protective layer.Preferably, the Re[590] of the retardation film is set such that the sumof the Re[590] of the retardation film and the Rth[590] of the firstprotective layer (Re[590]+Rth[590]) is from 220 nm to 300 nm. Forexample, when the first protective layer is substantially opticallyisotropic and when the |Rth[590]| is less than 10 nm, the Re[590] of theretardation film is preferably from 250 nm to 310 nm. When the Rth[590]of the first protective layer is 40 nm, the Re[590] of the retardationfilm is preferably from 180 nm to 260 nm. When the Rth[590] of the firstprotective layer is 60 nm, the Re[590] of the retardation film ispreferably from 160 nm to 240 nm. When the Rth[590] of the firstprotective layer is 100 nm, the Re[590] of the retardation film ispreferably from 120 nm to 200 nm.

The wave dispersion (D) of the retardation film is preferably from 0.90to 1.10, more preferably from 0.95 to 1.05, particularly preferably from0.98 to 1.02. The wave dispersion (D) is a value calculated from theformula: Re[480]/Re[590], wherein Re[480] and Re[590] are in-planeretardations measured at 23° C. and light wavelengths of 480 nm and 590nm, respectively. The use of the retardation film with a wave dispersion(D) in the above range allows the production of a liquid crystal displayin which the amount of color shift in an oblique direction (Δa*b*) issignificantly smaller than that in a liquid crystal display using aconventional retardation film.

The Nz coefficient of the retardation film is preferably from 0.1 to0.7, more preferably from 0.2 to 0.6, particularly preferably from 0.25to 0.55, most preferably from 0.35 to 0.55, wherein Re[590] is itsin-plane retardation measured at 23° C. and a light wavelength of 590nm, and Rth[590] is its retardation in its thickness direction that ismeasured at 23° C. and a light wavelength of 590 nm. Setting the Nzcoefficient in the above range allows the production of liquid crystaldisplays with very low level of color shift and light leakage in obliquedirections.

An appropriate value may be chosen as the Nz coefficient of theretardation film, depending on the Rth[590] of the first protectivelayer. For example, when the first protective layer is substantiallyoptically isotropic and when the |Rth[590]| is less than 10 nm, the Nzcoefficient of the retardation film is preferably from 0.4 to 0.6. Whenthe Rth[590] of the first protective layer is 40 nm, the Nz coefficientof the retardation film is preferably from 0.3 to 0.5. When the Rth[590]of the first protective layer is 60 nm, the Nz coefficient of theretardation film is preferably from 0.2 to 0.4. When the Rth[590] of thefirst protective layer is 100 nm, the Nz coefficient of the retardationfilm is preferably from 0.1 to 0.3.

An appropriate value may be chosen as the Rth[590] of the retardationfilm, depending on the Nz coefficient. In a preferred mode, the Rth[590]of the retardation film is smaller than the Re[590] and preferably from10 nm to 200 nm, more preferably from 20 nm to 180 nm, still morepreferably from 30 nm to 140 nm. Setting the Rth[590] in the above rangeallows the production of liquid crystal displays with very low level ofcolor shift and light leakage in oblique directions.

C-3. Methods for Producing Retardation Films

For example, the retardation film may be produced by a process includingthe steps of bonding a shrinkable film to both sides of the polymer filmcontaining the norbornene resin and heating and stretching the laminateby a longitudinal uniaxial stretching method with a roll drawingmachine. The shrinkable films are used in order to apply a shrinkageforce in a direction perpendicular to the stretching direction duringheating and stretching and to increase the refractive index (nz) in thethickness direction. Any appropriate method may be used to bond theshrinkable film to both sides of the polymer film. Methods includingplacing a pressure-sensitive adhesive layer containing an acrylicpressure-sensitive adhesive between the shrinkable film and the polymerfilm and bonding them are preferred in view of a high level ofproductivity, workability and cost-effectiveness.

An exemplary method for producing the retardation film will be describedwith reference to FIG. 3, which is a schematic diagram showing theconcept of a typical process for manufacturing the retardation film foruse in the invention. For example, while a polymer film 402 is fed froma first feeder 401, shrinkable films 404 and 406 each having apressure-sensitive adhesive layer are fed from a second feeder 403 and athird feeder 405, respectively and bonded to both sides of the polymerfilm 402 by means of laminating rolls 407 and 408. While the polymerfilm with the shrinkable films bonded to its both sides is kept at aconstant temperature by heating means 409 and receives a tension in themachine direction from rolls 410, 411, 412, and 413 in differentcircumferential velocities (and also receives a tension in the thicknessdirection from the shrinkable films at the same time), it is subjectedto a stretching process. The shrinkable films 404 and 406 each with thepressure-sensitive adhesive layer are separated from the stretched film418 by means of a first winding part 414 and a second winding part 415,respectively, and the stretched film 418 is wound on a third windingpart 419.

The shrinkable film is preferably a stretched film such as abiaxially-stretched film and a uniaxially-stretched film. For example,the shrinkable film may be obtained by stretching a sheet-shapedunstretched extruded film in the machine direction and/or the transversedirection at a specific ratio with a simultaneous biaxial stretchingmachine or the like. The forming and stretching conditions may beappropriately chosen depending on the composition, the type or thepurpose of the resin used.

Examples of a material for the shrinkable film include polyester,polystyrene, polyethylene, polypropylene, polyvinyl chloride, andpolyvinylidene chloride. The shrinkable film is preferably apolypropylene-containing, biaxially-stretched film. Such a shrinkablefilm has a high level of shrink uniformity and heat resistance and thuscan have a desired retardation value and can form a retardation filmwith good optical uniformity.

In an embodiment of the invention, the shrinkage rate S¹⁴⁰[MD] of theshrinkable film at 140° C. in its machine direction is preferably from5.0% to 7.7%, and the shrinkage rate S¹⁴⁰[TD] of the shrinkable film at140° C. in its transverse direction is preferably from 10.0% to 15.5%.More preferably, the shrinkable film has an S¹⁴⁰[MD] of 5.5% to 7.0% andan S¹⁴⁰[TD] of 11.5% to 14.5%.

In another embodiment of the invention, the shrinkage rate S¹⁶⁰[MD] ofthe shrinkable film at 160° C. in its machine direction is preferablyfrom 15.5% to 23.5%, and the shrinkage rate S¹⁶⁰[TD] of the shrinkablefilm at 140° C. in its transverse direction is preferably from 36.5% to54.5%. More preferably, the shrinkable film has an S¹⁶⁰[MD] of 17.5% to21.5% and an S¹⁶⁰[TD] of 40.0% to 50.0%. Setting the shrinkage rate ofthe shrinkable film in the above range at each temperature allows theproduction of retardation films with a desired retardation value andgood uniformity.

In an embodiment of the invention, the difference between the shrinkagerate of the shrinkable film at 140° C. in the transverse direction andthat in the machine direction (ΔS¹⁴⁰=S¹⁴⁰[TD]−S¹⁴⁰[MD]) is preferablyfrom 5.0% to 7.7%, more preferably from 5.7% to 7.0%. In anotherembodiment of the invention, the difference between the shrinkage rateof the shrinkable film at 160° C. in the transverse direction and thatin the machine direction (ΔS¹⁶⁰=S¹⁶⁰[TD]−S¹⁶⁰[MD]) is preferably from20.5% to 31.5%, more preferably from 23.0% to 28.5%. If the shrinkagerate is too large in the MD direction, not only the stretching tensionbut also the shrinkage force of the shrinkable film can be applied tothe stretching machine so that uniform stretching can be difficult.Setting the shrinkage rate of the shrinkable film in the above rangeallows uniform stretching with no excessive load on the equipment suchas the stretching machine.

The shrinkage stress T¹⁴⁰[TD] of the shrinkable film at 140° C. in thetransverse direction is preferably from 0.50 N/2 mm to 0.80 N/2 mm, morepreferably from 0.58 N/2 mm to 0.72 N/2 mm. The shrinkage stressT¹⁵⁰[TD] of the shrinkable film at 150° C. in the transverse directionis preferably from 0.60 N/2 mm to 0.90 N/2 mm, more preferably from 0.67N/2 mm to 0.83 N/2 mm. Setting the shrinkage rate of the shrinkable filmin the above range allows the production of retardation films with adesired retardation value and good optical uniformity.

The shrinkage rates S[MD] and S[TD] may be determined according to theheat shrinkage A method of JIS Z 1712 (1997), except that 140° C. (or160° C.) is used as the heating temperature in place of 120° C. and thata load of 3 g is applied to the test piece. Specifically, five 20mm-wide, 150 mm-long test pieces are sampled along each of the machinedirection [MD] and the transverse direction [TD] and each finished byputting gauge marks about 100 mm apart at the central portion. The testpieces are vertically hung with a load of 3 g applied thereto in an aircirculation type drying oven kept at a temperature of 140° C.±3° C. (or160° C.±3° C.), heated for 15 minutes and then taken out. The testpieces are then allowed to stand under the standard conditions (roomtemperature) for 30 minutes. The distance between the gauge marks isthen measured with a vernier caliper according to JIS B 7507, and theaverage of five measurements is calculated. The shrinkage rate may becalculated according to the formula: S(%)=[{(the distance (mm) betweenthe gauge marks before heating)−(the distance (mm) between the gaugemarks after heating)}/{(the distance (mm) between the gauge marks beforeheating)}]×100.

The shrinkable film to be used may be appropriately selected fromcommercially available shrinkable films for general packaging, foodpackaging, palette packaging, shrink labels, cap seals, electricinsulation, and other applications, as long as they satisfy thecharacteristics described above such as the shrinkage rate. Suchcommercially available shrinkable films may be used without modificationor after subjected to a secondary process such as a stretching orshrinking process. Examples of such commercially available shrinkablefilms include ALPHAN series manufactured by Oji paper Co., Ltd. (such asALPHAN P, ALPHAN S, and ALPHAN H (trade names)), FANCYTOP seriesmanufactured by Gunze Ltd. (such as FANCYTOP EP1 and FANCYTOP EP2 (tradenames)), TORAYFAN BO series manufactured by Toray Industries, Inc. (suchas TORAYFAN BO 2570, 2873, 2500, 2554, M114, and M304 (trade names)),SunTox-OP series manufactured by SunTox Co., Ltd. (such as PA20, PA21and PA30 (trade names)), and TOHCELLO OP series manufactured by TOHCELLOCo., Ltd. (such as TOHCELLO OPU-0, OPU-1 and OPU-2 (trade names)).

The temperature in the stretching oven during the heating and stretchingof the laminate of the shrinkable films and the polymer film containingthe norbornene resin (also referred to as stretching temperature) may beappropriately chosen depending on the desired retardation value and thetype and thickness of the polymer film used and so on. The stretchingtemperature is preferably in the range of Tg+1° C. to Tg+30° C. withrespect to the glass transition temperature (Tg) of the polymer film. Inthis range, the retardation value can be easily made uniform over theretardation film, and the film can resist crystallization (gettingclouded). Specifically, the stretching temperature is generally from110° C. to 185° C. The glass transition temperature (Tg) may bedetermined by DSC method according to JIS K 7121 (1987).

In the process of stretching the laminate of the shrinkable films andthe polymer film containing the norbornene resin, the stretch ratio(draw ratio) may be appropriately chosen depending on the desiredretardation value and the type and thickness of the polymer film and soon. The draw ratio is generally more than 1 and not more than 2, basedon the original length. In the stretching process, the feed speed isgenerally from 1 m/minute to 20 m/minute in view of the machine accuracyor stability of the stretching system. Under the stretching conditionsdescribed above, the desired retardation value can be achieved, andretardation films with a high level of optical uniformity can beobtained.

D. First Pressure-Sensitive Adhesive Layer

The first pressure-sensitive adhesive layer for use in the inventioncontains a pressure-sensitive adhesive that may be produced bycrosslinking a composition including at least a (meth)acrylate(co)polymer and a crosslinking agent including a peroxide as a maincomponent. As used herein, the term “pressure-sensitive adhesive” refersto a viscoelastic material that shows detectable adhesion at roomtemperature by pressure contact.

Referring to FIG. 1, a first pressure-sensitive adhesive layer 41 isplaced one side of the retardation film 30 which is opposite to the sidewhere the polarizing plate 20 is provided. The first pressure-sensitiveadhesive layer is used to fix the laminated film, for example, to aliquid crystal cell of a liquid crystal display. Such apressure-sensitive adhesive layer may be allowed to strongly adhere tothe stretched film (retardation film) containing the norbornene resin.The pressure-sensitive adhesive layer can also provide practicallysufficient adhesive properties and adhesion time to the substrate (glassplate) of the liquid crystal cell without causing peeling or bubbleseven in a high-temperature, high-humidity environment. At the same time,the pressure-sensitive adhesive layer can be separated from the liquidcrystal cell by a small force with no pressure-sensitive adhesive layeror retardation film left on the surface of the liquid crystal cell.

Pressure-sensitive adhesive layers that exhibit strong adhesion tonorbornene resin-containing stretched films and moderate adhesion andeasy peelability to substrates (glass plates) for liquid crystal cellsare not conventionally available. This may because the content of apolar group capable of acting on pressure-sensitive adhesives is lowerin norbornene resin-containing stretched films than in other resins suchas polycarbonate.

In addition, as described above, norbornene resin-containing stretchedfilms themselves are brittle so that peeling thereof can be moredifficult. According to the invention, however, a specificpressure-sensitive adhesive that may be produced by crosslinking aspecific composition is used so that liquid crystal display panels witha high level of adhesion and easy peelability can be obtained.

D-1. Physical Properties of First Pressure-Sensitive Adhesive Layer

The first pressure-sensitive adhesive layer may have any appropriatethickness, which is chosen depending on the purpose. The thickness ofthe first pressure-sensitive adhesive layer is preferably from 2 μm to50 μm, more preferably from 2 μm to 40 μm, particularly preferably from5 μm to 35 μm. Setting the thickness of the pressure-sensitive adhesivelayer in the above range allows production of the laminated film thathas moderate adhesion and a high level of easy peelability.

The transmittance of the first pressure-sensitive adhesive layer ispreferably 90% or more when measured at a light wavelength of 590 nm and23° C. The transmittance has a theoretical upper limit of 100% and apossible upper limit of 96%.

The Re[590] of the first pressure-sensitive adhesive layer is preferablyless than 2 nm, more preferably less than 1 nm. The Rth[590] of thepressure-sensitive adhesive layer is preferably less than 2 nm, morepreferably less than 1 nm.

The adhesive force (F_(1A)) of the first pressure-sensitive adhesivelayer to a glass plate at 23° C. is preferably from 2 N/25 mm to 10 N/25mm, more preferably from 3 N/25 mm to 9 N/25 mm, particularly preferablyfrom 3 N/25 mm to 8 N/25 mm, most preferably from 4 N/25 mm to 6 N/25mm. The adhesive force may be measured by a process that includespressing a laminated film with a width of 25 mm against a glass plate byone reciprocation of a 2 kg roller to bond the laminate to the glassplate, aging the laminated film at 23° C. for 1 hour, and then measuringan adhesive strength when the laminated film is peeled in a 90-degreedirection at a rate of 300 mm/minute, wherein the adhesive strength isdetermined as the adhesive force.

The anchoring force (F_(1B)) of the pressure-sensitive adhesive layer tothe retardation film at 23° C. is preferably from 10 N/25 mm to 40 N/25mm, more preferably from 14 N/25 mm to 40 N/25 mm, particularlypreferably from 17 N/25 mm to 35 N/25 mm. The anchoring force may bemeasured by a process that includes pressing a laminate of thepressure-sensitive adhesive layer and the retardation film each with awidth of 25 mm against the surface of an indium tin oxide (ITO)vapor-deposited onto a polyethylene terephthalate film by onereciprocation of a 2 kg roller to bond the laminate to the polyethyleneterephthalate film, aging the laminate at 23° C. for 1 hour, and thenmeasuring an adhesive strength when the polyethylene terephthalate filmis peeled together with the pressure-sensitive adhesive layer in a180-degree direction at a rate of 300 mm/minute, wherein the adhesivestrength is determined as the anchoring force.

In the laminated film of the invention, the adhesive force (F_(1A)) ofthe pressure-sensitive adhesive layer to a glass plate at 23° C. and theanchoring force (F_(1B)) of the pressure-sensitive adhesive layer to theretardation film at 23° C. preferably have the relation F_(1A)<F_(1B).The difference (F_(1B)−F_(1A)) between the anchoring force and adhesiveforce of the pressure-sensitive adhesive layer is preferably 5 N/25 mmor more, more preferably from 5 N/25 mm to 37 N/25 mm, particularlypreferably from 8 N/25 mm to 31 N/25 mm, most preferably from 16 N/25 mmto 30 N/25 mm. If F_(1A) and F_(1B) have the relation as describedabove, the pressure-sensitive adhesive layer can be separated from aliquid crystal cell with no pressure-sensitive adhesive layer orretardation film left on the surface of the liquid crystal cell, andliquid crystal display panels with a high level of adhesion and easypeelability can be obtained.

The first pressure-sensitive adhesive layer may further contain anyappropriate additive. Examples of such an additive include metal powder,glass fibers, glass beads, silica, and fillers. The pressure-sensitiveadhesive layer may also contain a material transferred from the adjacentlayer (such as a residual solvent, an additive and an oligomer). Thecontent of the additive is preferably more than 0 and not more than 10parts by weight, based on 100 parts by weight of the total solids of thepressure-sensitive adhesive layer. The content of the transferredmaterial is preferably more than 0 and not more than 5 parts by weight,based on 100 parts by weight of the total solids of thepressure-sensitive adhesive layer.

D-2. Pressure-Sensitive Adhesive for Forming First Pressure-SensitiveAdhesive Layer

The pressure-sensitive adhesive for forming the first pressure-sensitiveadhesive layer may be produced by crosslinking a composition includingat least a (meth)acrylate (co)polymer and a crosslinking agent includinga peroxide as a main component. As used herein, the term “crosslinking”refers to forming a three-dimensional network structure by chemicalbridging of a polymer.

D-3. Preparation of Raw Material Composition (for FirstPressure-Sensitive Adhesive Layer)

Any appropriate (meth)acrylate (co)polymer may be used depending on thepurpose. The term “(meth)acrylate (co)polymer” refers to a (co)polymerproduced with any (meth)acrylate monomer(s). When the polymer is acopolymer, the polymer may be a random copolymer, a block copolymer or agraft copolymer, while its molecule may have any structural arrangement.The (meth)acrylate (co)polymer is preferably a random copolymer in termof its polymer sequence.

As used herein, the term “(meth)acrylate (co)polymer” means an acrylatepolymer or a methacrylate polymer when the polymer is a homopolymer, orit means an acrylate copolymer synthesized from two or more acrylatemonomers, a methacrylate copolymer synthesized from two or moremethacrylate monomers, or a copolymer synthesized from one or moreacrylate monomers and one or more methacrylate monomers when the polymeris a copolymer. The term “(meth)acrylate monomer” means an acrylatemonomer or a methacrylate monomer.

The (meth)acrylate (co)polymer may be produced by any appropriatepolymerization method. Examples of the polymerization method include asolution polymerization method, a bulk polymerization method and asuspension polymerization method. In the invention, the polymerizationmethod is preferably a solution polymerization method. Specifically, thesolution polymerization method may include adding 0.01 to 0.2 parts byweight of a polymerization initiator such as azobisisobutyronitrile to asolution of 100 parts by weight of a monomer or monomers in a solventand allowing the mixture to react for 8 hours to 30 hours in a nitrogenatmosphere while setting the solution at a temperature of 50° C. to 70°C. Such a polymerization method is advantageous in that thepolymerization temperature can be controlled with high precision. It isalso advantageous in that the polymer solution can be easily taken outfrom the reaction vessel after the polymerization.

The weight average molecular weight (Mw) of the (meth)acrylate(co)polymer may be set at any appropriate value. When measured by a gelpermeation chromatography (GPC) method using tetrahydrofuran as asolvent, the weight average molecular weight (Mw) is preferably1,000,000 or more, more preferably from 1,200,000 to 3,000,000,particularly preferably from 1,200,000 to 2,500,000. The weight averagemolecular weight (Mw) may be appropriately adjusted by controlling thetype of the solvent, the polymerization temperature, the additive, andso on.

The (meth)acrylate (co)polymer is preferably a (co)polymer produced witha (meth)acrylate monomer(s) having a straight or branched alkyl group of1 to 10 carbon atoms. Examples of the (meth)acrylate monomer having astraight or branched alkyl group of 1 to 10 carbon atoms include methyl(meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl(meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate,n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl(meth)acrylate, isohexyl (meth)acrylate, n-heptyl (meth)acrylate,isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl(meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate,isononyl (meth)acrylate, n-decyl (meth)acrylate, and isodecyl(meth)acrylate.

The (meth)acrylate (co)polymer is more preferably a copolymer of a(meth)acrylate monomer having a straight or branched alkyl group of 1 to8 carbon atoms and another (meth)acrylate monomer having a straight orbranched alkyl group of 1 to 8 carbon atoms in which at least onehydrogen atom is replaced with a hydroxyl group. Such a copolymer ishighly reactive with the crosslinking agent mainly composed of aperoxide and thus can form a pressure-sensitive adhesive with goodadhesive properties.

The number of carbon (C₁) atoms in the alkyl group of the (meth)acrylatemonomer having the straight or branched alkyl group (in the unit havingthe alkyl group with no hydroxyl substituent) is preferably from 2 to 8,more preferably from 2 to 6, particularly preferably from 4 to 6. Thenumber of carbon (C₂) atoms in the alkyl group of the (meth)acrylatemonomer having the straight or branched alkyl group in which at leastone hydrogen atom is replaced with a hydroxyl group (in the unit havingthe alkyl group substituted with a hydroxyl group(s)) is preferablyequal to or more than that of the above, more preferably from 2 to 8,particularly preferably from 4 to 6. If the number of carbon atoms inthe alkyl group is controlled as described above, the reactivity of themonomer with the crosslinking agent can be increased so that apressure-sensitive adhesive with better adhesive properties can beobtained.

In particular, the (meth)acrylate (co)polymer is preferably a copolymerof a (meth)acrylate monomer having a straight or branched alkyl group of1 to 8 carbon atoms and another (meth)acrylate monomer having a straightor branched alkyl group of 1 to 8 carbon atoms in which at least onehydrogen atom is replaced with a hydroxyl group, and the copolymerpreferably contains 0.1% by mole to 10.0% by mole of a unit derived fromthe (meth)acrylate monomer having a straight or branched alkyl group of1 to 8 carbon atoms in which at least one hydrogen atom is replaced witha hydroxyl group. The content of the unit derived from the(meth)acrylate monomer having a straight or branched alkyl group of 1 to8 carbon atoms in which at least one hydrogen atom is replaced with ahydroxyl group is more preferably from 0.2% by mole to 5.0% by mole,particularly preferably from 0.3% by mole to 1.1% by mole.

Examples of the (meth)acrylate monomer having a straight or branchedalkyl group of 1 to 8 carbon atoms in which at least one hydrogen atomis replaced with a hydroxyl group include 2-hydroxyethyl (meth)acrylate,3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,4-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate,2-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate,3-hydroxy-3-methylbutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate,7-hydroxyheptyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate.

Any appropriate crosslinking agent including a peroxide as a maincomponent may be used as the crosslinking agent described above. Theperoxide is used to generate radicals by thermal decomposition and tocrosslink the (meth)acrylate (co)polymer. Examples of the peroxideinclude hydroperoxides, dialkyl peroxides, peroxyesters, diacylperoxides, peroxydicarbonates, peroxyketals, and ketone peroxides.Specific examples of the peroxide includedi(2-ethylhexyl)peroxydicarbonate,di(4-tert-butylcyclohexyl)peroxydicarbonate, tert-butylperoxyneodecanoate, tert-hexyl peroxypivalate, tert-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide,1,1,3,3-tetramethylbutylperoxy-2-ethyl hexanoate,di(4-methylbenzoyl)peroxide, dibenzoyl peroxide,tert-butylperoxybutyrate, benzoyl-m-methylbenzoyl peroxide, andm-toluoyl peroxide. One or more of these peroxides may be used singly orin any combination.

The crosslinking agent preferably includes a diacyl peroxide, morepreferably dibenzoyl peroxide and/or benzoyl-m-methylbenzoyl peroxide.Such peroxides typically have a half-life of one minute at a temperatureof 90° C. to 140° C. and thus have good storage stability and allowhigh-precision control of the crosslinking reaction.

A commercially available product may be used as the crosslinking agentwithout modification, or a mixture of a commercially available productand a solvent and/or an additive may be used as the crosslinking agent.Examples of commercially available crosslinking agents each including aperoxide as a main component include PEROYL series manufactured by NOFCORPORATION (such as PEROYL IB, 335, L, SA, IPP, NPP, and TCP (tradenames)) and NYPER series manufactured by NOF CORPORATION (such as NYPERFF, BO, NS, E, BMT-Y, BMT-K40, and BMT-M (trade names)).

The crosslinking agent may have any appropriate content, which is chosendepending on the purpose. The content of the crosslinking agent ispreferably from 0.01 to 1.0 part by weight, more preferably from 0.05 to0.8 parts by weight, particularly preferably from 0.1 to 0.5 parts byweight, most preferably from 0.15 to 0.45 parts by weight, based on 100parts by weight of the (meth)acrylate (co)polymer. Setting the contentof the crosslinking agent in the above range allows the production ofpressure-sensitive adhesive layers having good adhesive properties andlow moisture content, and as a result, liquid crystal display panelswith a high level of adhesion and easy peelability can be obtained.

In an embodiment of the invention, the composition may further includean isocyanate group-containing compound and/or a silane coupling agent.The isocyanate group-containing compound may be used to increase theadhesive strength (also referred to as anchoring force) at the interfacebetween the first pressure-sensitive adhesive layer and the retardationfilm. The silane coupling agent may be used to increase the adhesion tothe substrate of the liquid crystal cell.

Any appropriate isocyanate group-containing compound may be chosen asthe isocyanate group-containing compound described above. Examples ofthe isocyanate group-containing compound include tolylene diisocyanate,chlorophenylene diisocyanate, hexamethylene isocyanate, tetramethyleneisocyanate, isophorone diisocyanate, xylylene diisocyanate,diphenylmethane isocyanate, and trimethylolpropane xylene diisocyanate.Examples thereof also include adduct type isocyanate compounds,isocyanurate compounds and biuret type compounds each prepared with anyof the above isocyanate group-containing compounds. One or more of theseisocyanate group-containing compounds may be used singly or in anycombination. Trimethylolpropane xylene diisocyanate is preferably usedas the isocyanate group-containing compound for the firstpressure-sensitive adhesive layer.

A commercially available product may be used as the isocyanategroup-containing compound without modification. Alternatively, acommercially available isocyanate group-containing compound may be mixedwith a solvent or an additive before use. Examples of the commerciallyavailable isocyanate group-containing compound include TAKENATE seriesmanufactured by Mitsui Takeda Chemicals, Inc. (such as TAKENATE 500, 600and 700 (trade names)) and Coronate series manufactured by NipponPolyurethane Industry Co., Ltd. (such as Coronate L, MR, EH, and HL(trade names)).

The isocyanate group-containing compound may have any appropriatecontent, which is chosen depending on the purpose. The content of theisocyanate group-containing compound is preferably from 0.005 to 1.0part by weight, more preferably from 0.008 to 0.8 parts by weight,particularly preferably from 0.01 to 0.5 parts by weight, mostpreferably from 0.015 to 0.2 parts by weight, based on 100 parts byweight of the (meth)acrylate (co)polymer. Setting the content of theisocyanate group-containing compound in the above range allows theproduction of liquid crystal display panels that resist peeling at theinterface between the pressure-sensitive adhesive layer and theretardation film even in a more severe high-temperature, high-humidityenvironment.

A silane coupling agent having any appropriate functional group may bechosen as the silane coupling agent described above. Examples of such afunctional group include vinyl, epoxy, methacryloxy, amino, mercapto,acryloxy, acetoacetyl, isocyanate, styryl, and polysulfide groups.Examples of the silane coupling agent include vinyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,p-styryltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane,γ-acryloxypropyltrimethoxysilane,N-β(aminoethyl)γ-aminopropyltrimethoxysilane,γ-aminopropylmethoxysilane, γ-mercaptopropylmethyldimethoxysilane,bis(triethoxysilylpropyl)tetrasulfide, andγ-isocyanatepropyltrimethoxysilane. The silane coupling agent for use inthe first pressure-sensitive adhesive layer is preferably an acetoacetylgroup-containing silane coupling agent.

A commercially available product may be used as the silane couplingagent without modification. Alternatively, a solvent or an additive maybe added to a commercially available silane coupling agent before use.Examples of the commercially available silane coupling agent include KAseries manufactured by Shin-Etsu Chemical Co., Ltd. (such as KA-1003(trade name)), KBM series manufactured by Shin-Etsu Chemical Co., Ltd.(such as KBM-303, KBM-403 and KBM-503 (trade names)), KBE seriesmanufactured by Shin-Etsu Chemical Co., Ltd. (such as KBE-402, KBE-502and KBE-903 (trade names)), SH series manufactured by TORAY INDUSTRIES,INC. (such as SH6020, SH6040 and SH6062 (trade names)), and SZ seriesmanufactured by TORAY INDUSTRIES, INC. (such as SZ6030, SZ6032 andSZ6300 (trade names)).

The silane coupling agent may have any appropriate content, which ischosen depending on the purpose. The content of the silane couplingagent is preferably from 0.001 to 2.0 parts by weight, more preferablyfrom 0.005 to 2.0 parts by weight, particularly preferably from 0.01 to1.0 part by weight, most preferably from 0.02 to 0.5 parts by weight,based on 100 parts by weight of the (meth)acrylate (co)polymer. Settingthe content of the silane coupling agent in the above range allows theproduction of liquid crystal display panels that are free from peelingor bubbles even in a more severe high-temperature, high-humidityenvironment.

In an embodiment of the invention, the composition is prepared by amethod including Steps 1-A and 1-B described below.

Step 1-A: the step of diluting the (meth)acrylate (co)polymer with asolvent to prepare a polymer solution (1-A); and

Step 1-B: the step of adding the crosslinking agent mainly composed ofthe peroxide, the isocyanate group-containing compound, and the silanecoupling agent to the polymer solution (1-A) obtained in Step 1-A toprepare a polymer solution (1-B).

Steps 1-A and 1-B are each performed in order that a homogeneouscomposition may be obtained by dispersing or dissolving the addedmaterial or materials. When the (meth)acrylate (co)polymer is producedby a solution polymerization method, the resulting reaction solution maybe used as the polymer solution (1-A) without modification.Alternatively, the resulting reaction solution may be diluted by addinga solvent thereto and then used.

Any solvent with which the (meth)acrylate (co)polymer can be uniformlydiluted to form a solution is preferably used as the solvent describedabove. Examples of the solvent include toluene, xylene, chloroform,dichloromethane, dichloroethane, phenol, diethyl ether, tetrahydrofuran,anisole, tetrahydrofuran, acetone, methyl isobutyl ketone, methyl ethylketone, cyclohexanone, cyclopentanone, 2-hexanone, 2-pyrrolidone,N-methyl-2-pyrrolidone, n-butanol, 2-butanol, cyclohexanol, isopropylalcohol, tert-butyl alcohol, glycerol, ethylene glycol, diethyleneglycol dimethyl ether, 2-methyl-2,4-pentanediol, dimethylformamide,dimethylacetamide, acetonitrile, butyronitrile, methyl cellosolve,methyl cellosolve acetate, ethyl acetate, and butyl acetate. The solventis preferably toluene or ethyl acetate. These solvents are highlyproducible, workable and economical.

The polymer solution (1-B) preferably has a total solids content of 1%by weight to 40% by weight, more preferably of 5% by weight to 30% byweight. Setting the total solids content in the above range allows theproduction of a solution with good coatability to substrates so that apressure-sensitive adhesive layer with good surface uniformity can beobtained.

Besides the above components, the composition may also contain anyappropriate additive. Examples of the additive include a plasticizer, aheat stabilizer, a light stabilizer, a lubricant, an antioxidant, anultraviolet absorbing agent, a flame retardant, a colorant, anantistatic agent, a compatibilizing agent, a crosslinking agent, and athickener. The additive may have any appropriate content (in weightratio), which is set depending on the purpose. Preferably, the contentof the additive is more than 0 and not more than 5 parts by weight,based on 100 parts by weight of the (meth)acrylate (co)polymer. Anyappropriate method may be used to add each material in the process ofpreparing the composition. In a preferred mode, the composition may beprepared by adding the crosslinking agent mainly composed of theperoxide, the isocyanate group-containing compound and the silanecoupling agent in this order to the (meth)acrylate (co)polymer. If oneor both of the isocyanate group-containing compound and the silanecoupling agent are not added, the step of addition thereof will beomitted.

D-4. Method for Crosslinking the Composition (for FirstPressure-Sensitive Adhesive Layer)

Any appropriate method may be used to crosslink the composition,depending on the purpose. A method including heating the composition ata temperature of 50° C. to 200° C. is preferably used. The heatingtemperature is preferably from 70° C. to 190° C., more preferably from100° C. to 180° C., particularly preferably from 120° C. to 170° C. Ifthe heating temperature is set in the above range, the crosslinkingreaction between the peroxide and the polymer can rapidly occur with noside reaction so that a pressure-sensitive adhesive with good adhesiveproperties can be obtained.

When the heating method is used to crosslink the composition, anyappropriate heating time may be used. The heating time is preferablyfrom 5 seconds to 20 minutes, more preferably from 5 seconds to 10minutes, particularly preferably from 10 seconds to 5 minutes. Settingthe heating time in the above range allows an efficient crosslinkingreaction between the peroxide and the polymer.

In an embodiment of the invention, the composition is crosslinked by amethod including Steps 1-A and 1-B described above and then Steps 1-Cand 1-D described below.

Step 1-C: the step of applying the polymer solution (1-B) obtained inStep 1-B; and

Step 1-D: the step of drying the coating obtained in Step 1-C at atemperature of 50° C. to 200° C. to form a pressure-sensitive adhesivelayer on the surface of a substrate.

Step 1-C may be performed in order that a thin film-shaped coating maybe obtained by thinly spreading the polymer solution on a substrate.Step 1-D may be performed in order to evaporate the solvent from thecoating and to crosslink the peroxide and the polymer. The drying may beperformed in a multistage manner using a plurality of temperaturecontrol means set at different temperatures, respectively. By such amethod, a pressure-sensitive adhesive layer can be efficiently obtainedwith less variation in thickness, and the crosslinking reaction betweenthe peroxide and the polymer can be properly performed so that apressure-sensitive adhesive layer with good adhesive properties can beobtained.

A coating method using any appropriate coater may be used to apply thepolymer solution (1-B) to a substrate. Examples of the coater include areverse roll coater, a forward roll coater, a gravure coater, a knifecoater, a rod coater, a slot orifice coater, a curtain coater, afountain coater, an air doctor coater, a kiss coater, a dip coater, abead coater, a blade coater, a cast coater, a spray coater, a spincoater, an extrusion coater, and a hot melt coater. Preferred coatersinclude a reverse roll coater, a gravure coater, a slot orifice coater,a curtain coater, and a fountain coater. A coating with good surfaceuniformity can be obtained by a coating method using any of the abovecoaters.

Any appropriate substrate may be chosen as the substrate describedabove, depending on the purpose. The substrate to be used preferably hasa release-treated surface on the side where the polymer solution (1-B)will be applied. A polymer film is preferably used as the substrate,because it allows roll production and can significantly increase theproductivity. The substrate may be the retardation film used in theinvention or any other polymer film. The substrate is preferably apolyethylene terephthalate film treated with a silicone release agent.In this mode, the substrate may be used as a release liner for the film,and the release liner is peeled off before the laminated film ispractically used.

Any appropriate temperature control means may be used to heat and drythe composition. Examples of the temperature control means include anair circulation type thermostatic oven with circulated hot air or coldair, a heater using a microwave, a far infrared ray or the like, and aroll, heat pipe roll or metal belt heated for temperature control.

In an embodiment of the invention, the pressure-sensitive adhesive layeris laminated by a method further including Step 1-E described belowafter Steps 1-A to 1-D.

Step 1-E: the step of transferring, to the retardation film, thepressure-sensitive adhesive layer formed on the surface of the substrateby Step 1-D to form a laminate.

Such a method allows the production of a laminated film which resistschanges in the optical properties of the retardation film and has a highlevel of optical properties. The pressure-sensitive adhesive layer maybe separated from the substrate and then transferred to the retardationfilm, may be transferred to the retardation film while separated fromthe substrate, or may be transferred to the retardation film and thenseparated from the substrate. After this process, a highly uniformlaminate of the pressure-sensitive adhesive layer and the retardationfilm can be obtained.

When the first pressure-sensitive adhesive layer used in the inventioncontains a pressure-sensitive adhesive that may be produced bycrosslinking the composition containing the isocyanate group-containingcompound, the pressure-sensitive adhesive layer is preferably aged by amethod further including Step 1-F after Step 1-E.

Step 1-F: the step of storing the laminate obtained in Step 1-E for atleast three days.

Step 1-F is performed in order to age the pressure-sensitive adhesivelayer. As used herein, the term “age (or aging)” means that thepressure-sensitive adhesive layer is allowed to stand (stored) underappropriate conditions for a certain period of time so that thediffusion or chemical reaction of the substances in thepressure-sensitive adhesive layer is allowed to proceed to producepreferred properties or states.

Any appropriate temperature may be chosen as the temperature for agingthe pressure-sensitive adhesive layer (aging temperature), depending onthe type of the polymer or the crosslinking agent, the aging time periodand so on. The aging temperature is preferably from 10° C. to 80° C.,more preferably from 20° C. to 60° C., particularly preferably from 20°C. to 40° C. If the above temperature range is selected, apressure-sensitive adhesive layer with stable adhesive properties can beobtained.

Any appropriate time may be chosen as the time for aging thepressure-sensitive adhesive layer (aging time), depending on the type ofthe polymer or the crosslinking agent, the aging temperature and so on.The aging time is preferably 3 days or more, more preferably 5 days ormore, particularly preferably 7 days or more. If the above time isselected, a pressure-sensitive adhesive layer with stable adhesiveproperties can be obtained.

An example of the method for producing the first pressure-sensitiveadhesive layer is described with reference to FIG. 6. FIG. 6 is aschematic diagram illustrating the concept of a typical process forforming the first pressure-sensitive adhesive layer for use in theinvention. For example, a silicone release agent-treated polyethyleneterephthalate film 502 is fed as a substrate from a first feeder 501 andcoated at a coater unit 503 with the polymer solution (1-B) which isprepared by adding the crosslinking agent mainly composed of a peroxide,the isocyanate group-containing compound and the silane coupling agentto the polymer solution (1-A) prepared by diluting the (meth)acrylate(co)polymer with a solvent. The coating formed on the surface of thesubstrate is fed to a temperature controller (drying means) 504 anddried and crosslinked, for example, at a temperature of 50° C. to 200°C., resulting in a pressure-sensitive adhesive layer. A retardation film506 is fed from a second feeder 506 and transferred to thepressure-sensitive adhesive layer on laminating rolls 507 and 508. Theresulting laminate 509 of the retardation film, the pressure-sensitiveadhesive layer and the silicone release agent-treated polyethyleneterephthalate film 502 is wound on a winding part 510. The siliconerelease agent-treated polyethylene terephthalate film 502 is used byitself as a release liner.

D-5. Physical and Chemical Properties of the First Pressure-SensitiveAdhesive Layer

The pressure-sensitive adhesive that may be obtained by the methoddescribed above (accordingly, the first pressure-sensitive adhesivelayer) is preferably characterized by the physical and chemicalproperties described below.

The pressure-sensitive adhesive preferably has a gel fraction of 40% to90%, more preferably of 50% to 90%, particularly preferably of 60% to85%. If the gel fraction is set in the above range, a pressure-sensitiveadhesive layer with good adhesive properties can be obtained. Whenimmersed in a solvent, a part where the polymer of thepressure-sensitive adhesive is crosslinked and has a three-dimensionalnetwork structure (also referred to as a gel part) generally absorbs thesolvent to increase its volume. This phenomenon is called swelling. Thegel fraction may be a value measured by the method described in thesection “EXAMPLES.”

The pressure-sensitive adhesive preferably has a glass transitiontemperature (Tg) of −70° C. to −10° C., more preferably of −60° C. to−20° C., particularly preferably of −50° C. to −30° C. Setting the glasstransition temperature in the above range allows the production of apressure-sensitive adhesive layer that has strong adhesion to theretardation film and has moderate adhesion and a high level of easypeelability to the substrate (a glass plate) of a liquid crystal cell.

The pressure-sensitive adhesive preferably has a moisture content of1.0% or less, more preferably of 0.8% or less, particularly preferablyof 0.6% or less, most preferably of 0.4%. The theoretical lower limit ofthe moisture content is zero. Setting the moisture content in the aboverange allows the production of a pressure-sensitive adhesive layer thatresists foaming even in a high-temperature environment. The moisturecontent may be a value determined by a process that includes placing thepressure-sensitive adhesive layer in an air circulation typethermostatic oven at 150° C. and determining the weight loss ratio aftera lapse of one hour.

E. second Pressure-Sensitive Adhesive Layer

In a preferred embodiment of the invention, the laminated film furtherincludes a second pressure-sensitive adhesive layer between thepolarizing plate and the retardation film. FIG. 5 is a schematiccross-sectional view of a laminated film according to an embodiment ofthe invention. It should be noted that the length, width and thicknessof each component in FIG. 1 are not shown in a true ratio forconvenience of easy reference. This laminated film 11 includes at leasta polarizing plate 20, a second pressure-sensitive adhesive layer 42,retardation film 30, and a first pressure-sensitive adhesive layer 41,provided in this order. The polarizing plate 20 includes a polarizer 21,a first protective layer 21 placed on a side of the polarizer 21 wherethe retardation film 30 is provided, and a second protective layer 23placed on another side of the polarizer 21 which is opposite to the sidewhere the retardation film 30 is provided. The retardation film 30 is astretched film which includes a norbornene resin. The firstpressure-sensitive adhesive layer 41 includes a pressure-sensitiveadhesive that may be produced by crosslinking a composition whichincludes a (meth)acrylate (co)polymer and a crosslinking agentcomprising a peroxide as a main component. The second pressure-sensitiveadhesive layer includes a pressure-sensitive adhesive that may beproduced by crosslinking a composition comprising a (meth)acrylate(co)polymer, a silane coupling agent, and a crosslinking agentcomprising an isocyanate group-containing compound as a main component.

E-1. Physical Properties of Second Pressure-Sensitive Adhesive Layer

The second pressure-sensitive adhesive layer may have any appropriatethickness, which is chosen depending on the purpose. The thickness ofthe pressure-sensitive adhesive layer is preferably from 2 μm to 50 μm,more preferably from 2 μm to 40 μm, particularly preferably from 5 μm to35 μm. Setting the thickness of the pressure-sensitive adhesive layer inthe above range allows the production of pressure-sensitive adhesivelayer with a with good adhesive properties.

The transmittance of the second pressure-sensitive adhesive layer ispreferably 90% or more when measured at a light wavelength of 590 nm and23° C. The transmittance has a theoretical upper limit of 100% and apossible upper limit of 96%.

The Re[590] of the second pressure-sensitive adhesive layer ispreferably less than 2 nm, more preferably less than 1 nm. The Rth[590]of the pressure-sensitive adhesive layer is preferably less than 2 nm,more preferably less than 1 nm.

The adhesive force (F_(2A)) of the pressure-sensitive adhesive layer toa glass plate at 23° C. is preferably from 8 N/25 mm to 40 N/25 mm, morepreferably from 6 N/25 mm to 40 N/25 mm, particularly preferably from 10N/25 mm to 35 N/25 mm.

The adhesive force may be measured by a process that includes pressing a25 mm width of polarizing plate with pressure-sensitive adhesive layeragainst a glass plate by one reciprocation of a 2 kg roller to bond thelaminate to the glass plate, aging the laminate at 23° C. for 1 hour,and then measuring an adhesive strength when the polarizing plate withpressure-sensitive adhesive layer is peeled in a 90-degree direction ata rate of 300 mm/minute, wherein the adhesive strength is determined asthe adhesive force.

The anchoring force (F_(2B)) of the second pressure-sensitive adhesivelayer to the polarizing plate (to the first protective layer) at 23° C.is preferably from 10 N/25 mm to 40 N/25 mm, more preferably from 13N/25 mm to 40 N/25 mm, particularly preferably from 16 N/25 mm to 35N/25 mm. The anchoring force may be measured by a process that includespressing a laminate of a pressure-sensitive adhesive layer and apolarizing plate each with a width of 25 mm against the surface of anindium tin oxide vapor-deposited onto a polyethylene terephthalate filmby one reciprocation of a 2 kg roller to bond the laminate to thepolyethylene terephthalate film, aging the laminate at 23° C. for 1hour, and then measuring an adhesive strength when the polyethyleneterephthalate film is peeled together with the pressure-sensitiveadhesive layer in a 180-degree direction at a rate of 300 mm/minute,wherein the adhesive strength is determined as the anchoring force.

In the laminated film of the invention, the adhesive force (F_(1A)) ofthe first pressure-sensitive adhesive layer to a glass plate at 23° C.,the anchoring force (F_(1B)) of the first pressure-sensitive adhesivelayer to the retardation film at 23° C., the adhesive force (F_(2A)) ofthe second pressure-sensitive adhesive layer to a retardation film at23° C., and the adhesive force (F_(2B)) of the second pressure-sensitiveadhesive layer to a polarizing plate (to a first protective layer)retardation film at 23° C. are set to have a relation that F_(1A) isminimum, have a relation, for example, F_(1A)<F_(2A)≦F_(2B).

In a preferred embodiment of the invention, the difference(F_(2A)−F_(1A)) between the anchoring force (F_(2A)) of the secondpressure-sensitive adhesive layer at 23° C. to the retardation film andthe adhesive force (F_(1A)) of the first pressure-sensitive adhesivelayer at 23° C. to a glass plate is preferably 3N/25 mm or more, morepreferably from 3 N/25 mm to 37 N/25 mm, particularly preferably from 4N/25 mm to 37 N/25 mm, most preferably from 5 N/25 mm to 31 N/25 mm. IfF_(2A) and F_(1A) have the relation as described above, thepressure-sensitive adhesive layer with easy peelability can be obtained,thus can be separated from a liquid crystal cell with nopressure-sensitive adhesive layer or retardation film left on thesurface of the liquid crystal cell.

In another preferred embodiment of the invention, the difference(F_(2B)−F_(1A)) between the anchoring force (F_(2B)) of the secondpressure-sensitive adhesive layer at 23° C. to the polarizing plate (tothe first protective layer) and the adhesive force (F_(1A)) of the firstpressure-sensitive adhesive layer at 23° C. to a glass plate ispreferably 5N/25 mm or more, more preferably from 5 N/25 mm to 40 N/25mm, particularly preferably from 6 N/25 mm to 37 N/25 mm, mostpreferably from 6 N/25 mm to 31 N/25 mm. If F_(2B) and F_(1A) have therelation as described above, the pressure-sensitive adhesive layer witheasy peelability can be obtained, thus can be separated from a liquidcrystal cell with no pressure-sensitive adhesive layer or retardationfilm left on the surface of the liquid crystal cell.

The second pressure-sensitive adhesive layer may further contain anyappropriate additive. Examples of such an additive include metal powder,glass fibers, glass beads, silica, and fillers. The pressure-sensitiveadhesive layer may also contain a material transferred from the adjacentlayer (such as a residual solvent, an additive and an oligomer). Thecontent of the additive is preferably more than 0 and not more than 10parts by weight, based on 100 parts by weight of the total solids of thepressure-sensitive adhesive layer. The content of the transferredmaterial is preferably more than 0 and not more than 5 parts by weight,based on 100 parts by weight of the total solids of thepressure-sensitive adhesive layer.

The pressure-sensitive adhesive for forming the secondpressure-sensitive adhesive layer may be produced by crosslinking acomposition comprising a (meth)acrylate (co)polymer, a silane couplingagent, and a crosslinking agent comprising an isocyanategroup-containing compound as a main component.

Any appropriate (meth)acrylate (co)polymer may be used depending on thepurpose. The term “(meth)acrylate (co)polymer” refers to a (co)polymerproduced with any (meth)acrylate monomer(s). When the polymer is acopolymer, the polymer may be a random copolymer, a block copolymer or agraft copolymer, while its molecule may have any structural arrangement.The (meth)acrylate (co)polymer is preferably a random copolymer in termof its polymer sequence. The (meth)acrylate (co)polymer may be producedby the method described in the section D-3.

The weight average molecular weight (Mw) of the (meth)acrylate(co)polymer may be set at any appropriate value. When measured by a gelpermeation chromatography (GPC) method using tetrahydrofuran as asolvent, the weight average molecular weight (Mw) is preferably1,000,000 or more, more preferably from 1,200,000 to 3,000,000,particularly preferably from 1,200,000 to 2,500,000. The weight averagemolecular weight (Mw) may be appropriately adjusted by controlling thetype of the solvent, the polymerization temperature, the additive, andso on.

Examples of the (meth)acrylate (co)polymer that may be used are the sameas described in the section D-3. The (meth)acrylate (co)polymer ispreferably a copolymer of a (meth)acrylate monomer having a straight orbranched alkyl group of 1 to 8 carbon atoms and another (meth)acrylatemonomer having a straight or branched alkyl group of 1 to 8 carbon atomsin which at least one hydrogen atom is replaced with a hydroxyl group.Such a copolymer is highly reactive with the crosslinking agent mainlycomposed of a peroxide and thus can form a pressure-sensitive adhesivewith good adhesive properties.

The number of carbon (C₁) atoms in the alkyl group of the (meth)acrylatemonomer having the straight or branched alkyl group (in the unit with nohydroxyl substituent) is preferably from 2 to 8, more preferably from 2to 6, particularly preferably from 4 to 6. The number of carbon (C₂)atoms in the alkyl group of the (meth)acrylate monomer having thestraight or branched alkyl group in which at least one hydrogen atom isreplaced with a hydroxyl group (in the unit substituted with a hydroxylgroup(s)) is preferably less than that of the C₁ above, more preferablyfrom 2 to 4, particularly preferably 2. If the number of carbon atoms inthe alkyl group is controlled as described above, the reactivity of themonomer with the crosslinking agent can be increased so that apressure-sensitive adhesive with better adhesive properties can beobtained.

In particular, the (meth)acrylate (co)polymer is preferably a copolymerof a (meth)acrylate monomer having a straight or branched alkyl group of1 to 8 carbon atoms and another (meth)acrylate monomer having a straightor branched alkyl group of 1 to 8 carbon atoms in which at least onehydrogen atom is replaced with a hydroxyl group, and the copolymerpreferably contains 0.05% by mole to 0.25% by mole of a unit derivedfrom the (meth)acrylate monomer having a straight or branched alkylgroup of 1 to 8 carbon atoms in which at least one hydrogen atom isreplaced with a hydroxyl group. The content of the unit derived from the(meth)acrylate monomer having a straight or branched alkyl group of 1 to8 carbon atoms in which at least one hydrogen atom is replaced with ahydroxyl group is more preferably from 0.10% by mole to 0.22% by mole,particularly preferably from 0.14% by mole to 1.20% by mole.

Examples of the (meth)acrylate monomer having a straight or branchedalkyl group of 1 to 8 carbon atoms in which at least one hydrogen atomis replaced with a hydroxyl group include 2-hydroxyethyl (meth)acrylate,3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,4-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate,2-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate,3-hydroxy-3-methylbutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate,7-hydroxyheptyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate.

Any appropriate crosslinking agent including comprising an isocyanategroup-containing compound as a main component may be used as thecrosslinking agent described above. The isocyanate group-containingcompound may be used is the same as described in the section D-3.

Any appropriate content may be chosen as the content of the crosslinkingagent. The content of the crosslinking agent is preferably from 0.15 to1.0 part by weight, more preferably from 0.30 to 0.90 parts by weight,particularly preferably from 0.39 to 0.81 parts by weight, mostpreferably from 0.48 to 0.72 parts by weight, based on 100 parts byweight of the (meth)acrylate (co)polymer. Setting the content of thecrosslinking agent in the above range allows strong adhesion to theretardation film even in a high-temperature, high-humidity environment.

Examples of the silane coupling agent may be used are the same asdescribed in the section D-3. The silane coupling agent for use in thefirst pressure-sensitive adhesive layer is preferably an epoxygroup-containing silane coupling agent, more preferablyglycidoxypropyltrimethoxysilane.

The silane coupling agent may have any appropriate content, which ischosen depending on the purpose. The content of the silane couplingagent is preferably from 0.01 to 0.20 parts by weight, more preferablyfrom 0.037 to 0.113 parts by weight, particularly preferably from 0.049to 0.101 part by weight, most preferably from 0.060 to 0.090 parts byweight, based on 100 parts by weight of the (meth)acrylate (co)polymer.Setting the content of the silane coupling agent in the above rangeallows the production of liquid crystal display panels that are freefrom peeling or bubbles even in a more severe high-temperature,high-humidity environment.

In an embodiment of the invention, the composition is prepared by amethod including Steps 2-A and 2-B described below.

Step 2-A: the step of diluting the (meth)acrylate (co)polymer with asolvent to prepare a polymer solution (2-A); and

Step 2-B: the step of adding the isocyanate group-containing compound,and the silane coupling agent to the polymer solution (2-A) obtained inStep 2-A to prepare a polymer solution (2-B).

Steps 2-A and 2-B are each performed in order that a homogeneouscomposition may be obtained by dispersing or dissolving the addedmaterial or materials. When the (meth)acrylate (co)polymer is producedby a solution polymerization method, the resulting reaction solution maybe used as the polymer solution (2-A) without modification.Alternatively, the resulting reaction solution may be diluted by addinga solvent thereto and then used.

Examples of the solvent may be used are the same as described in thesection D-3. The solvent is preferably toluene or ethyl acetate, andbutyl acetate. The solvent is preferably toluene or ethyl acetate. Thesesolvents are highly producible, workable and economical. These solventsare highly producible, workable and economical.

The polymer solution (2-B) preferably has a total solids content of 5%by weight to 50% by weight, more preferably of 10% by weight to 40% byweight. Setting the total solids content in the above range allows theproduction of a solution with good coatability to substrates so that apressure-sensitive adhesive layer with good surface uniformity can beobtained.

Besides the above components, the composition may also contain anyappropriate additive. Examples of the additive used are the same asdescribed in the section D-3. Preferably, the content of the additive ismore than 0 and not more than 5 parts by weight, based on 100 parts byweight of the (meth)acrylate (co)polymer. (meth)acrylate (co)polymer.

Any appropriate method may be used to add each material in the processof preparing the composition. In a preferred mode, the composition maybe prepared by adding the crosslinking agent mainly composed of theisocyanate group-containing compound and the silane coupling agent inthis order to the (meth)acrylate (co)polymer.

E-4. Method for Crosslinking the Composition (for FirstPressure-Sensitive Adhesive Layer)

Any appropriate method may be used to crosslink the composition,depending on the purpose. A method including heating the composition ata temperature of 20° C. to 200° C. is preferably used. The heatingtemperature is preferably from 50° C. to 170° C. Setting the heatingtemperature in the above range allows a production of an adhesive layerwith good surface uniformity.

When the heating method is used to crosslink the composition, anyappropriate heating time may be used. The heating time is preferablyfrom 10 seconds to 20 minutes, more preferably from 20 seconds to 10minutes, particularly preferably from 30 seconds to 5 minutes. Settingthe heating time in the above range allows a production of an adhesivelayer with good surface uniformity.

In an embodiment of the invention, the composition is crosslinked by amethod including Steps 2-A and 2-B described above and then Steps 2-Cand 2-D described below.

Step 2-C: the step of applying the polymer solution (2-B) obtained inStep 1-B; and

Step 2-D: the step of drying the coating obtained in Step 2-C at atemperature of 20° C. to 200° C. to form a pressure-sensitive adhesivelayer on the surface of a substrate.

Step 2-C may be performed in order that a coating layer with lessvariation in thickness can be obtained. Step 2-D may be performed inorder to evaporate the solvent from the coating layer. The drying may beperformed in a multistage manner using a plurality of temperaturecontrol means set at different temperatures, respectively. By such amethod, a pressure-sensitive adhesive layer can be efficiently obtainedwith less variation in thickness.

Coating methods using appropriate coaters, substrates, and temperaturecontrol means, described in the section D-4 may be used as a coatingmethod, a substrate, and a temperature control mean for the polymersolution (2-B), respectively.

In an embodiment of the invention, the pressure-sensitive adhesive layeris laminated and aged by a method further including Step 2-E and 2-Fdescribed below after Steps 2-A to 2-D.

Step 2-E: the step of transferring, to the retardation film, thepressure-sensitive adhesive layer formed on the surface of the substrateby Step 2-D to form a laminate.

Step 2-F: the step of storing the laminate obtained in Step 1-E for atleast three days.

Such a method allows the production of a laminated film which resistschanges in the optical properties of the retardation film and has a highlevel of optical properties. The pressure-sensitive adhesive layer maybe separated from the substrate and then transferred to the retardationfilm, may be transferred to the retardation film while separated fromthe substrate, or may be transferred to the retardation film and thenseparated from the substrate. After this process, a highly uniformlaminate of the pressure-sensitive adhesive layer and the retardationfilm can be obtained. Step 1-F is performed in order to age thepressure-sensitive adhesive layer.

Any appropriate temperature may be chosen as the temperature for agingthe pressure-sensitive adhesive layer (aging temperature), depending onthe type of the polymer or the crosslinking agent, the aging time periodand so on. The aging temperature is preferably from 10° C. to 80° C.,more preferably from 20° C. to 60° C., particularly preferably from 20°C. to 40° C. If the above temperature range is selected, apressure-sensitive adhesive layer with stable adhesive properties can beobtained.

Any appropriate time may be chosen as the time for aging thepressure-sensitive adhesive layer (aging time), depending on the type ofthe polymer or the crosslinking agent, the aging temperature and so on.The aging time is preferably 3 days or more, more preferably 5 days ormore, particularly preferably 7 days or more. If the above time isselected, a pressure-sensitive adhesive layer with stable adhesiveproperties can be obtained.

E-5. Physical and Chemical Properties of the Second Pressure-SensitiveAdhesive Layer

The pressure-sensitive adhesive that may be obtained by the methoddescribed above (accordingly, the second pressure-sensitive adhesivelayer) is preferably characterized by the physical and chemicalproperties described below.

The pressure-sensitive adhesive preferably has a gel fraction of 60% to96%, more preferably of 70% to 94%, particularly preferably of 78% to92%. If the gel fraction is set in the above range, anpressure-sensitive adhesive layer that has strong adhesion to theretardation film and has good adhesive properties to the substrate (aglass plate) of a liquid crystal cell.

The pressure-sensitive adhesive preferably has a glass transitiontemperature (Tg) of −42° C. to −14° C., more preferably of −37° C. to−18° C., particularly preferably of −34° C. to −21° C. Setting the glasstransition temperature in the above range allows the production of apressure-sensitive adhesive layer with good adhesive properties.

The pressure-sensitive adhesive preferably has a moisture content of0.4% or more, more preferably of 0.4% to 0.8%. The theoretical lowerlimit of the moisture content is zero. Setting the moisture content inthe above range allows the production of a pressure-sensitive adhesivelayer that has good adhesive properties to the retardation film. Themoisture content may be a value determined by a process that includesplacing the pressure-sensitive adhesive layer in an air circulation typethermostatic oven at 150° C. and determining the weight loss ratio aftera lapse of one hour.

F. Liquid Crystal Display Panel

FIGS. 6( a) and 6(b) are schematic cross-sectional view of liquidcrystal display panels according to preferred embodiments of theinvention. It should be noted that the length, width and thickness ofeach component in FIGS. 6( a) and 6(b) are not shown in a true ratio forconvenience of easy reference.

Referring to FIG. 6( a), a liquid crystal panel 100 includes a liquidcrystal cell 50 and a laminated film 10 according to the invention onone side of the liquid crystal cell 50. Preferably, a reflecting film(not shown) or a second polarizing plate (not shown) may be placed onthe other side of the liquid crystal cell 50. When the second polarizingplate is placed, it is preferably placed such that the direction of itsabsorption axis is substantially orthogonal to the direction of theabsorption axis of the polarizer 21. As used herein, the term“substantially orthogonal” is intended to include the case where theangle between the directions of the absorption axes of the polarizer 21and the second polarizing plate (polarizer) is 90°±2.0°, preferably90°±1.0°, more preferably 90°±0.5°. In an embodiment of the invention,the polarizers placed on both sides of the liquid crystal cell may bethe same or different.

Referring to FIG. 6( b), a liquid crystal panel 101 includes a liquidcrystal cell 50, a laminated film 10 according to the invention on oneside of the liquid crystal cell 50, and another laminated film 10′according to the invention on another side of the liquid crystal cell50. The laminated film 20 is preferably placed such that the directionof the absorption axis of the polarizer 21 is substantially orthogonalto the direction of the absorption axis of the polarizer 21′. The term“substantially orthogonal” is intended to include the case where theangle between the directions of the absorption axes of the polarizer 21and the second polarizing plate (polarizer) is 90°±2.0°, preferably90°±1.0°, more preferably 90°±0.5°. In an embodiment of the invention,the laminated films 10 and 10′ may be the same or different.

Referring to FIG. 1, the liquid crystal cell 50 for use in the inventionincludes a pair of substrates 51 and 51′ and a liquid crystal layer 12serving as a display medium sandwiched between the substrates 51 and51′. One substrate (active matrix substrate) 51′ is provided with aswitching element (typically TFT) for controlling the electro-opticalproperties of the liquid crystal, scanning lines for supplying gatesignals to the active element, and signal lines for supplying sourcesignals to the active element (all not shown). The other substrate(color filter substrate) 51 is provided with a color filter.Alternatively, the color filter may be placed on the active matrixsubstrate 51′. Alternatively, the color filter may be omitted, forexample, in a field sequential system where three color (RGB) lightsources are used as lighting means for a liquid crystal display. Thedistance between the substrates 51 and 51′ (cell gap) is controlled bymeans of spacers (not shown). An alignment film (not shown), which isfor example made of polyimide, is provided on the side of the substrate51 or 51′ to be in contact with the liquid crystal layer 52.

F. Liquid Crystal Display

FIG. 7 is a schematic cross-sectional view of a liquid crystal displayaccording to a preferred embodiment of the invention. It should be notedthat the length, width and thickness of each component in FIG. 7 is notshown in a true ratio for convenience of easy reference. The liquidcrystal display 200 includes a liquid crystal display panel 100 (or 101)and a backlight unit 80 placed on one side of the liquid crystal displaypanel 100. While a direct type backlight unit is used in the illustratedexample, it may be replaced with another type such as a sidelight type.When a direct type is used, the backlight unit 80 may include at least abacklight 81, a reflecting film 82, a diffusing plate 83, a prism sheet84, and a brightness enhancement film 85. When a sidelight type is used,the backlight unit may include at least the above components and alight-guiding plate and a light reflector. The use of these opticalcomponents allows the production of a liquid crystal display with betterdisplay characteristics. As long as the effects of the invention areachieved, the optical components illustrated in FIG. 7 may be partiallyomitted or replaced with any other optical component, depending on thetype of illumination for the liquid crystal display, the drive mode ofthe liquid crystal cell, or any other application.

The liquid crystal display may be a transmissive liquid crystal display,in which the screen is viewed while light is applied to the backside ofthe liquid crystal display panel, or a reflective liquid crystaldisplay, in which the screen viewed while light is applied to the viewerside of the liquid crystal display panel. Alternatively, the liquidcrystal display may be a transflective liquid crystal display, whichcombines the characteristics of a transmissive type with those of areflective type. The liquid crystal display of the invention ispreferably a transmissive one, because such a display can have arelatively high contrast ratio in oblique directions.

Any appropriate structure may be used for the backlight. The backlightstructure may be typically of “a direct type,” which applies light fromdirectly below a liquid crystal display panel, or “an edge-lightingtype,” which applies light from the side end of a liquid crystal displaypanel. The structure of the lighting means is preferably of a directtype, because the direct type backlight can achieve relatively highbrightness.

Any appropriate light source may be used for the backlight, depending onthe purpose. Examples of such a backlight source include cold cathodefluorescent tubes (CCFLs), light-emitting diodes (LEDs), organic ELdevices (OLEDs), and field emission devices (FEDs). When alight-emitting diode is used for the backlight, the light source mayproduce white or three colors RGB. When the light-emitting diodes areused as three color RGB light sources, a field sequential liquid crystaldisplay may be obtained which allows color display without colorfilters.

The reflecting film is used to prevent light from escaping to the sideopposite to the viewer side of the liquid crystal and to efficientlyintroduce light from the backlight into the light-guiding plate. Forexample, the reflecting film may be a silver-vapor-depositedpolyethylene terephthalate film or a laminated film composed ofmultilayers of polyester resin. The reflecting film preferably has areflectance of 90% or more over the wavelength range of 410 nm to 800nm. The reflecting film generally has a thickness of 50 μm to 200 μm. Acommercially available reflecting film may be used as the reflectingfilm without modification. Examples of the commercially availablereflecting film include REFWHITE series manufactured by Kimoto Co., Ltd.and Vikuiti ESR series manufactured by Sumitomo 3M Limited.

The light-guiding plate is used to distribute light from the backlightthroughout the screen. For example, the light-guiding plate may be atapered product of an acrylic resin, a polycarbonate resin, acycloolefin resin or the like whose thickness decreases as it goes awayfrom the light source.

The diffusing plate is used to guide the light from the light-guidingplate into a wide angle and to evenly brighten the screen. For example,the diffusing plate may be a roughened polymer film or a diffusingagent-containing polymer film. The diffusing plate preferably has a hazeof 85% to 92%. Additionally, the total light transmittance of thediffusing plate is 90% or more. A commercially available diffusing platemay be used as the diffusing plate without modification. Examples of thecommercially available diffusing plate include OPLUS series manufacturedby KEIWA Inc. and LIGHTUP series manufactured by Kimoto Co., Ltd.

The prism sheet is used to concentrate the wide-angle light from thelight-guiding plate in a specific direction and to enhance thebrightness of the liquid crystal display in the normal direction. Forexample, the prism sheet may be a laminate including a base film of apolyester resin and a prism layer of an acrylic resin or aphotosensitive resin stacked on the surface of the base film. Acommercially available prism sheet may be used as the prism sheetwithout modification. Examples of the commercially available prism sheetinclude DIAART series manufactured by Mitsubishi Rayon Co., Ltd.

The brightness enhancement film is used to enhance the brightness of theliquid crystal display in the normal and oblique directions. Acommercially available brightness enhancement film may be used withoutmodification. Examples of the commercially available brightnessenhancement film include NIPOCS PCF series manufactured by Nitto DenkoCorporation and Vikuiti DBEF series manufactured by Sumitomo 3M Limited.

G. Display Characteristics of Liquid Crystal Display

When a black image is displayed, the liquid crystal display includingthe liquid crystal display panel of the invention preferably has amaximum Y value of 0.5 or less, more preferably of 0.4 or less,particularly preferably of 0.3 or less, at a polar angle of 60° alongall azimuth angles (0° to 360°). When a black image is displayed, theliquid crystal display preferably has an average Y value of 0.3 or less,more preferably of 0.2 or less, particularly preferably of 0.1 or less,at a polar angle of 60° along all azimuth angles (0° to 360°). The Yvalue is a tristimulus value Y defined in the CIE 1931 XYZ system andhas a theoretical lower limit of 0. The fact that this value is smallerindicates that the amount of leakage of light in oblique directions issmaller when a black image is displayed on the screen of the liquidcrystal display.

When a black image is displayed, the liquid crystal display preferablyhas a maximum color shift (Δa*b*) of 8.0 or less, more preferably of 6.0or less, particularly preferably of 4.0 or less, at a polar angle of 60°along all azimuth angles (0° to 360°). When a black image is displayed,the liquid crystal display preferably has an average color shift (Δa*b*)of 4.0 or less, more preferably of 3.0 or less, particularly preferablyof 2.0 or less, at a polar angle of 60° along all azimuth angles (0° to360°). The Δa*b* is a value calculated from the formula:{(a*)2+(b*)2}^(1/2), wherein a* and b* are chromatic coordinates definedin the CIE 1976 L*a*b* color space. The Δa*b* has a theoretical lowerlimit of 0. The fact that this value is smaller indicates that changesin color in oblique directions are smaller when a black image isdisplayed on the screen of the liquid crystal display.

H. Uses of the Liquid Crystal Display of the Invention

The liquid crystal display of the invention may be used in anyappropriate application. Examples of the application include OAequipment such as personal computer monitors, notebook computers, andcopy machines; portable equipment such as cellular phones, watches,digital cameras, personal digital assistances (PDAs), and portable gamemachines; household appliance such as video cameras, televisions, andmicrowave ovens; vehicle equipment such as back monitors, monitors forcar navigation systems, and car audios; display equipment such asinformation monitors for stores; alarm systems such as surveillancemonitors; and care and medical equipment such as care monitors andmedical monitors.

The liquid crystal display of the invention is preferably used fortelevisions. In particular, the liquid crystal display of the inventionis preferably used for large-sized televisions. The screen size of suchtelevisions is preferably at least 17-inch wide (373 mm×224 mm), morepreferably at least 23-inch wide (499 mm×300 mm), particularlypreferably at least 26-inch wide (566 mm×339 mm), most preferably atleast 32-inch wide (687 mm×412 mm).

EXAMPLES

The invention is further described using the examples and thecomparative examples below, which are not intended to limit the scope ofthe invention. The analytical methods below were each used in theexamples.

(1) Method for Measuring the Single-Piece Transmittance, Degree ofPolarization, and Hue Values a and b of Polarizing Plate

The measurement was performed at 23° C. using a spectrophotometer DOT-3(trade name, manufactured by Murakami Color Research Laboratory).

(2) Method for Measuring Molecular Weights

Molecular weights were calculated by a gel permeation chromatography(GPC) method using polystyrene as a standard sample. Specifically, themeasurement was performed using the equipment, tools, measurementconditions, and samples below.

Measured samples: Each sample was dissolved in tetrahydrofuran to form a0.1% by weight solution. The solution was allowed to stand overnight andthen filtered through a 0.45 μm membrane filter. The resulting filtratewas used in the measurement.

Analytical equipment: “HLC-8120GPC” manufactured by Tosoh Corporation

-   Columns: TSK gel Super HM-H/H4000/H3000/H2000-   Column size: each 6.0 mm I.D.×150 mm-   Eluent: tetrahydrofuran-   Flow rate: 0.6 ml/minute-   Detector: RI-   Column temperature: 40° C.-   Injection amount: 20 μl    (3) Method for Measuring Thickness

For thicknesses of less than 10 μm, measurement was performed using aspectrophotometer for thin films, Instant Multi-Photometry System“MCPD-2000” (trade name, manufactured by Otsuka Electronics Co., Ltd.).For thicknesses of 10 μm or more, measurement was performed using adigital micrometer Model “KC-351C” (trade name, manufactured by AnritsuCompany).

(4) Method for Measuring the Average Refractive Index of Films

The measurement was performed using an Abbe refractometer “DR-M4” (tradename, manufactured by ATAGO CO., LTD.), and the average refractive indexwas determined from refractive indexes measured at 23° C. and a lightwavelength of 589 nm.

(5) Method for Measuring Retardations (Re[480], Re[590] and Rth[590])

The retardations were measured at 23° C. and light wavelengths of 480 nmand 590 nm using “KOBRA21-ADH” (trade name, manufactured by OjiScientific Instruments).

(6) Method for Measuring Transmittance (T[590])

The transmittance was measured at 23° C. and a light wavelength of 590nm using an ultraviolet-visible spectrophotometer “V-560” (product name,manufactured by JASCO Corporation).

(7) Method for Measuring Absolute Value of Photoelastic Coefficient(C[590])

While stress (5 to 15 N) was applied to a sample (2 cm×10 cm in size)supported at both ends, the retardation of the center of the sample wasmeasured (23° C./a wavelength of 590 nm) using a spectroscopicellipsometer “M-220” (product name, manufactured by JASCO Corporation).The photoelastic coefficient was calculated from the slope of a functionof the stress and the retardation.

(8) Method for Measuring Shrinkage Rate of Shrinkable Films

The shrinkage rate was determined according to the heat shrinkage Amethod of JIS Z 1712 (1997), except that 140° C. (or 160° C.) was usedas the heating temperature in place of 120° C. and that a load of 3 gwas applied to the test piece. Specifically, five 20 mm-wide, 150mm-long test pieces are sampled along each of the machine direction [MD]and the transverse direction [TD] and each finished by putting gaugemarks about 100 mm apart at the central portion. The test pieces werevertically hung with a load of 3 g applied thereto in an air circulationtype drying oven kept at a temperature of 140° C.±3° C. (or 160° C.±3°C.), heated for 15 minutes and then taken out. The test pieces were thenallowed to stand under the standard conditions (room temperature) for 30minutes. The distance between the gauge marks was then measured with avernier caliper according to JIS B 7507, and the average of fivemeasurements was calculated. The shrinkage rate was calculated accordingto the formula: S(%)=[{(the distance (mm) between the gauge marks beforeheating)−(the distance (mm) between the gauge marks afterheating)}/{(the distance (mm) between the gauge marks beforeheating)}]×100.

(9) Method for Measuring Shrinkage Stress of Shrinkable Film

The shrinkage stress T¹⁴⁰[TD] at 140° C. in the transverse direction[TD] and the shrinkage stress T¹⁵⁰[TD] at 150° C. in the transversedirection [TD] were measured by TMA method using the equipment below.

-   Equipment: “TMA/SS 6100” manufactured by Seiko Instruments Inc.-   Data processing: “EXSTAR 6000” manufactured by Seiko Instruments    Inc.-   Measurement mode: constant temperature rising rate measurement (10°    C./minute)-   Measurement atmosphere: the air (23° C.)-   Load: 20 mN-   Sample size: 15 mm×2 mm (the long side is along the transverse    direction [TD])    (10) Method for Measuring the Adhesive Force of Pressure-Sensitive    Adhesive Layer

A 25-mm wide sample was pressed against a glass plate by onereciprocation of a 2 kg roller to bond the sample to the glass plate,then aged at 23° C. for 1 hour, and then measured for adhesive strengthwhen the sample was peeled in a 90-degree direction at a rate of 300mm/minute.

(11) Method for Measuring the Anchoring Force of Pressure-SensitiveAdhesive Layer

A laminate of the pressure-sensitive adhesive layer and the retardationfilm each with a width of 25 mm was pressed against the treated surfaceof an indium tin oxide (ITO)-vapor-deposited polyethylene terephthalatefilm (“125 Tetlight OES” (trade name) 125 μm in thickness, manufacturedby Oike & Co., Ltd.) by one reciprocation of a 2 kg roller to bond thelaminate to the polyethylene terephthalate film, then aged at 23° C. for1 hour, and then measured for adhesive strength when the polyethyleneterephthalate film was peeled together with the pressure-sensitiveadhesive layer in a 180-degree direction at a rate of 300 mm/minute.

(12) Method for Measuring the Glass Transition Temperature (Tg) ofPressure Sensitive Adhesive

According to JIS K 7121, the glass transition temperature was measuredby DSC method using a differential scanning calorimeter “DSC 220C”(product name) manufactured by Seiko Instruments Inc.

(13) Method for Measuring the Moisture Content of Pressure-SensitiveAdhesive

The pressure-sensitive adhesive layer was placed in an air circulationtype thermostatic oven at 150° C. and measured for weight loss after alapse of one hour. The moisture content of the pressure-sensitiveadhesive was calculated from the rate of the weight loss:{(W₁−W₂)/W₁}×100, wherein W₁ is the weight of the pressure-sensitiveadhesive layer before it is placed in the air circulation typethermostatic oven, and W₂ is the weight of the pressure-sensitiveadhesive layer after it is placed in the air circulation typethermostatic oven.

(14) Method for Measuring the Gel Fraction of Pressure-SensitiveAdhesive

A pressure-sensitive adhesive sample was measured for weight in advanceand placed in a vessel filled with ethyl acetate. The pressure-sensitiveadhesive sample was allowed to stand at 23° C. for 7 days and then takenout. After the solvent was wiped off the sample, its weight wasmeasured. Its gel fraction was calculated from the formula:{(W_(A)−W_(B))/W_(A)}×100, wherein W_(A) is the weight of thepressure-sensitive adhesive layer before it is placed in ethyl acetate,and W_(B) is the weight of the pressure-sensitive adhesive layer afterit is placed in ethyl acetate.

(15) Method for Measuring the Amount (Y) of Leakage of Light From Liquidcrystal display

After the light was turned on and allowed to run for 30 minutes in adark room at 23° C., tristimulus Y values defined in the CIE 1931 XYZsystem were measured with “EZ Contrast 160D” (product name) manufacturedby ELDIM along azimuth angles of 0° to 360° at a polar angle of 60° withrespect to the screen on which a black image was displayed. In themeasurement, the long side direction of the liquid crystal display panelwas defined as being at an azimuth angle of 0°, and the normal directionwas defined as being at a polar angle of 0°.

(16) Method for Measuring the Amount (Δa*b*) of Color Shift of LiquidCrystal Display

After the light was turned on and allowed to run for 30 minutes in adark room at 23° C., chromatic coordinates a* and b* defined in the CIE1976 L*a*b* color space were measured with “EZ Contrast 160D” (productname) manufactured by ELDIM along azimuth angles of 0° to 360° at apolar angle of 60° with respect to the screen on which a black image wasdisplayed. The amount of color shift (Δa*b*) in the oblique directionwas calculated from the formula: {(a*)2+(b*)2}^(1/2).

Preparation of Retardation Films

Reference Example 1

A shrinkable film A (a 60 μm-thick, polypropylene-containing,biaxially-stretched film (“TORAYFAN BO 2873” (trade name) manufacturedby TORAY INDUSTRIES, INC.) was bonded to both sides of a 100 μm-thickpolymer film containing a resin of a hydrogenated ring-opening polymerof a norbornene monomer (a norbornene resin) (“ZEONOR ZF-14-100” (tradename) 1.52 in average refractive index, 136° C. in Tg, 3.0 nm inRe[590], and 5.0 nm in Rth[590], manufactured by OPTES INC.) with anacrylic pressure-sensitive adhesive layer (15 μm in thickness)interposed therebetween. The laminated film was then held in the machinedirection of the film by means of a roll stretching machine andstretched to 1.38 times in an air circulation type oven at 146° C. Afterthe stretching, each shrinkable film A was separated together with eachacrylic pressure-sensitive adhesive layer so that a retardation film wasprepared. The retardation film was named Retardation Film A, and itsproperties are shown in Table 1. The retardation film had a refractiveindex ellipsoid satisfying the relation nx>nz>ny, and its wavedispersion (D) was 1.00. The physical properties of the shrinkable filmA are shown in Table 2.

TABLE 1 Retardation Film C × 10⁻¹² Stretching Conditions Re Rth(Absolute Shrinkable Temperature Ratio Thickness Nz [590] [590] Value)Film (° C.) (times) (μm) Coefficient (nm) (nm) (m²/N) Reference A 1461.38 A 108 0.50 270.0 135.0 3.1 Example 1 Reference A 140 1.08 B 1070.11 116.3 12.6 3.1 Example 2 Reference A 150 1.20 C 118 0.18 146.1 26.93.1 Example 3 Reference A 145 1.20 D 110 0.29 170.0 49.3 3.1 Example 4Reference A 146 1.38 E 147 0.36 194.0 69.8 5.2 Example 5 Reference A 1481.35 F 114 0.39 219.1 85.7 3.1 Example 6 Reference A 148 1.40 G 111 0.44245.1 106.6 3.1 Example 7 Reference B 146 1.43 H 144 0.52 288.0 150.05.2 Example 8 Reference C 146 1.42 I 141 0.60 271.0 163.0 5.2 Example 9Reference A 143 1.58 J 46 0.50 145.0 72.5 3.1 Example 10 Reference A 1431.52 K 47 0.47 132.0 62.0 3.1 Example 11 Reference A 143 1.45 L 48 0.46119.0 54.6 3.1 Example 12 Reference D 147 1.27 M 64 0.50 270.0 135.0 50Example 13

TABLE 2 Shrinkable Film A B C D Shrinkage Rate at 140° C. in (%) 6.4 — —5.7 Machine direction S¹⁴⁰ [MD] Shrinkage Rate at 140° C. in (%) 12.8 —— 7.6 Transverse Direction S¹⁴⁰ [TD] S¹⁴⁰ [TD]-S¹⁴⁰ [MD] (%) 6.4 — — 19Shrinkage Rate at 160° C. in (%) 19.6 19.7 17 18 Machine direction S¹⁶⁰[MD] Shrinkage Rate at 160° C. in (%) 45.5 45.3 39.7 35.7 TransverseDirection S¹⁶⁰ [TD] S¹⁶⁰ [TD]-S¹⁶⁰ [MD] (%) 25.9 25.6 22.7 17.7Shrinkage Stress at 140° C. in (N/2 mm) 0.65 0.63 0.54 0.45 TransverseDirection T¹⁴⁰[TD] Shrinkage Stress at 150° C. in (N/2 mm) 0.75 0.740.65 0.56 Transverse Direction T¹⁵⁰[TD]

Reference Examples 2, 3, 4, 6, and 7

Retardation Films B, C, D, F, and G were prepared using the process ofReference Example 1, except that the stretching conditions shown inTable 2 were used instead. The properties of the retardation films areshown in Table 1. These retardation films each had a refractive indexellipsoid satisfying the relation nx>nz>ny, and their wave dispersion(D) was 1.00.

Reference Example 5

A shrinkable film A was bonded to both sides of a 130 μm-thick polymerfilm (“ARTON FLZU 130D0” (trade name) 78,200 in weight average molecularweight, 1.53 in average refractive index, 135° C. in Tg, 3.0 nm inRe[590], and 5.0 nm in Rth[590], manufactured by JSR Corporation)containing a resin of a hydrogenated ring-opening polymer of anorbornene monomer (norbornene resin) with an acrylic pressure-sensitiveadhesive layer (15 μm in thickness) interposed therebetween. Thelaminated film was then held in the machine direction of the film bymeans of a roll stretching machine and stretched to 1.38 times in an aircirculation type oven at 146° C. After the stretching, each shrinkablefilm A was separated together with each acrylic pressure-sensitiveadhesive layer so that a retardation film (named Retardation Film E) wasprepared. Its properties are shown in Table 1. The retardation film hada refractive index ellipsoid satisfying the relation nx>nz>ny, and itswave dispersion (D) was 1.00.

Reference Example 8

Retardation Film H was prepared using the process of Reference Example5, except that the draw ratio was 1.43 times and that a shrinkable filmB (a 60 μm-thick, polypropylene-containing, biaxially-stretched film)was used instead. Its properties are shown in Table 1. This retardationfilm had a refractive index ellipsoid satisfying the relation nx>nz>ny,and its wave dispersion (D) was 1.00. The physical properties of theshrinkable film B are shown in Table 2.

Reference Example 9

Retardation Film I was prepared using the process of Reference Example5, except that the draw ratio was 1.42 times and that a shrinkable filmC (a 60 μm-thick, polypropylene-containing, biaxially-stretched film)was used instead. Its properties are shown in Table 1. This retardationfilm had a refractive index ellipsoid satisfying the relation nx>nz>ny,and its wave dispersion (D) was 1.00. The physical properties of theshrinkable film C are shown in Table 2.

Reference Examples 10, 11 and 12

Retardation Films J, K and L were prepared using the process ofReference Example 1, except that a 40 μm-thick polymer film (“ZEONORZF-14-40” (trade name) 1.52 in average refractive index, 136° C. in Tg,1.0 nm in Re[590], and 3.0 nm in Rth[590], manufactured by OPTES INC.)containing a resin of a hydrogenated ring-opening polymer of anorbornene monomer (norbornene resin) was used instead and that thestretch conditions were set as shown in Table 1. The properties of theseretardation films are shown in Table 1. These films each had arefractive index ellipsoid satisfying the relation nx>nz>ny, and theirwave dispersion (D) was 1.00.

Reference Example 13

A shrinkable film D (a 60 μm-thick, polypropylene-containing,biaxially-stretched film (“TORAYFAN BO 2570A” (trade name) manufacturedby TORAY INDUSTRIES, INC.) was bonded to both sides of a 55 μm-thickpolymer film (ELMEC (trade name) 60,000 in weight average molecularweight, 1.53 in average refractive index, 136° C. in Tg, 1.0 nm inRe[590], and 3.0 nm in Rth[590], manufactured by Kaneka Corporation)with an acrylic pressure-sensitive adhesive layer (15 μm in thickness)containing a polycarbonate resin interposed therebetween. The laminatedfilm was then held in the machine direction of the film by means of aroll stretching machine and stretched to 1.27 times in an aircirculation type oven at 147° C. After the stretching, each shrinkablefilm D was separated together with each acrylic pressure-sensitiveadhesive layer so that a retardation film (named Retardation Film M) wasprepared. Its properties are shown in Table 1. The retardation film hada refractive index ellipsoid satisfying the relation nx>nz>ny, and itswave dispersion (D) was 1.08. The physical properties of the shrinkablefilm D are shown in Table 2.

FIG. 8 is a graph showing the relationship between the in-planeretardation Re[590] and the Nz coefficient of each of the retardationfilms obtained in Reference Examples 1 to 12. FIG. 9 is a graph showingthe relationship between the in-plane retardation Re[590] and thethickness direction retardation Rth[590] of each of the retardationfilms obtained in Reference Examples 1 to 12. As shown above,retardation films having different retardation values and Nzcoefficients and also having a refractive index ellipsoid satisfying therelation nx>nz>ny were actually obtained using specific shrinkablefilms, specific stretching methods and specific stretching conditions.

Preparation of Polarizing Plates

Reference Example 14

A commercially available polarizing plate (“SIG1423DU” (trade name)manufactured by Nitto Denko Corporation) was used as Polarizing Plate Awithout modification. The polarizing plate includes a polarizer, a firstprotective layer placed on the liquid crystal cell side of thepolarizer, and a second protective layer placed on the side opposite tothe liquid crystal cell side. The first protective layer of PolarizingPlate A is substantially isotropic and has an Re[590] of 0.5 nm and anRth[590] of 1.0 nm.

Reference Example 15

A commercially available polarizing plate (“TEG1425DU” (trade name)manufactured by Nitto Denko Corporation) was used as Polarizing Plate Bwithout modification. The polarizing plate includes a polarizer, a firstprotective layer placed on the liquid crystal cell side of thepolarizer, and a second protective layer placed on the side opposite tothe liquid crystal cell side. The first protective layer of PolarizingPlate B has a refractive index ellipsoid satisfying the relationnx≈ny>nz and has an Re[590] of 1.3 nm and an Rth[590] of 39.8 nm.

TABLE 3 Reference Example 14 Reference Example 15 Polarizing Plate A BProperties Single-Piece 42.6 44.1 Transmittance (%) Degree ofPolarization 99.99 99.95 (%) Hue Value a −1.5 −1.5 Hue Value b 3.8 3.7Polarizer Materials Iodine-Containing Iodine-Containing PolyvinylAlcohol Film Polyvinyl Alcohol Film First Protective Layer MaterialsTriacetyl Cellulose Triacetyl Cellulose Second Protective MaterialsTriacetyl Cellulose Triacetyl Cellulose LayerPreparation of Pressure-Sensitive Adhesives

Reference Example 16

99 parts by weight of butyl acrylate, 1.0 part by weight of4-hydroxybutyl acrylate, 0.3 parts by weight of2,2-azobisisobutyronitrile, and ethyl acetate were added to a reactorvessel equipped with a cooling tube, a nitrogen introducing tube, athermometer, and a stirrer so that a solution was formed. While nitrogengas was blown into the solution, the solution was then subjected to apolymerization reaction at 60° C. for 4 hours to give an acrylatecopolymer of butyl acrylate and 4-hydroxybutyl acrylate with a weightaverage molecular weight of 1,650,000.

The acrylate copolymer was diluted with ethyl acetate to form a polymersolution (1-A) with a total solids content of 30% by weight. Then 0.2parts by weight of a dibenzoyl peroxide-containing crosslinking agent(“NYPER BO-Y” (trade name) manufactured by NOF CORPORATION), 0.02 partsby weight of trimethylolpropane-xylylene diisocyanate (“TAKENATE D110N”(trade name) manufactured by Mitsui Takeda Chemicals, Inc.), and 0.2parts by weight of an acetoacetyl group-containing silane coupling agent(“A-100” (trade name) manufactured by Soken Chemical & Engineering Co.,Ltd.), based on 100 parts by weight of the acrylate copolymer were addedto the polymer solution (1-A) so that a polymer solution (1-B) wasprepared. The polymer solution (1-B) was uniformly applied to thesurface of a silicone release agent-treated polyethylene terephthalatefilm (substrate) with a fountain coater and then dried in an aircirculation type thermostatic oven at 155° C. for 70 seconds so that apressure-sensitive adhesive layer was formed on the surface of thesubstrate. The pressure-sensitive adhesive layer formed on the substratesurface was then placed on the corona-treated (1.2 kW/15 m/minute)surface of the Retardation Film E to form a laminate. The laminate wasaged in an air circulation type thermostatic oven at 70° C. for 7 days.The resulting pressure-sensitive adhesive layer was namedPressure-Sensitive Adhesive Layer A (21 μm in thickness). Its propertiesare shown in Table 4. According to the invention, Retardation Film E maybe replaced with any of Retardation Films A to L shown in Table 2 orwith the polarizing plate shown in Table 3, and Pressure-SensitiveAdhesive Layer A may be placed thereon by the same method as describedin this section so that equivalent adhesive properties can be obtained.

TABLE 4 Reference Reference Reference Example 16 Example 17 Example 18Pressure-Sensitive Adhesive Layer A B C Adhesive Force to (N/25 mm) 6.04.7 10.2 Glass Plate (F_(1A)) Anchoring Force to (N/25 mm) 22.0 22.725.2 Retardation Film (F_(1B)) F_(1B) − F_(1A) (N/25 mm) 16.0 18.0 15.0Gel Fraction (%) 72 82 81 Glass Transition (° C.) −38.0 −38.0 −27.8Temperature Moisture Content (%) 0.25 0.27 1.2

Reference Example 17

Pressure Sensitive Adhesive Layer B (21 μm in thickness) was preparedemploying the process of Reference Example 16, except thattrimethylolpropane-xylylene diisocyanate (“TAKENATE D110N” (trade name)manufactured by Mitsui Takeda Chemicals, Inc.) was used in an amount of0.12 parts by weight, based on 100 parts by weight of the acrylatecopolymer. The properties of Pressure-Sensitive Adhesive Layer B areshown in Table 4. According to the invention, Retardation Film E may bereplaced with any of Retardation Films A to L shown in Table 2 or withthe polarizing plate shown in Table 3, and Pressure-Sensitive AdhesiveLayer B may be placed thereon by the same method as described in thissection so that equivalent adhesive properties can be obtained.

Reference Example 18

100 parts by weight of butyl acrylate, 5 parts by weight of acrylicacid, 0.075 parts by weight of 2-hydroxyethyl acrylate, 0.3 parts byweight of 2,2-azobisisobutyronitrile, and ethyl acetate were added to areactor vessel equipped with a cooling tube, a nitrogen introducingtube, a thermometer, and a stirrer so that a solution was formed. Whilenitrogen gas was blown into the solution, the solution was thensubjected to a polymerization reaction at 60° C. for 4 hours to give anacrylate copolymer of butyl acrylate, acrylic acid and 2-hydroxyethylacrylate with a weight average molecular weight of 2,200,000. Theacrylate copolymer was diluted with ethyl acetate to form a polymersolution (2-A) with a total solids content of 30% by weight. To thepolymer solution (2-A) were then added 0.6 parts by weight of acrosslinking agent mainly composed of an isocyanate group-containingcompound (“Coronate L” (trade name) manufactured by Nippon PolyurethaneIndustry Co., Ltd.) and 0.075 parts by weight ofγ-glycidoxypropyltrimethoxysilane (“KBM-403” (trade name) manufacturedby Shin-Etsu Chemical Co., Ltd.) in this order, based on 100 parts byweight of the acrylate copolymer, so that a polymer solution (2-B) wasprepared.

The polymer solution (2-B) was uniformly applied to the surface of asilicone release agent-treated polyethylene terephthalate film(substrate) with a fountain coater and then dried in an air circulationtype thermostatic oven at 155° C. for 70 seconds so that apressure-sensitive adhesive layer was formed on the surface of thesubstrate. The pressure-sensitive adhesive layer formed on the substratesurface was placed on the corona-treated (1.2 kW/15 m/minute) surface ofthe Retardation Film E to form a laminate. The laminate was aged in anair circulation type thermostatic oven at 23° C. for 7 days. Theresulting pressure-sensitive adhesive layer was named Pressure-SensitiveAdhesive Layer C (21 μm in thickness). Its properties are shown in Table4. According to the invention, Retardation Film E may be replaced withany of Retardation Films A to L shown in Table 2 or with the polarizingplate shown in Table 3, and Pressure-Sensitive Adhesive Layer C may beplaced thereon by the same method as described in this section so thatequivalent adhesive properties can be obtained.

Preparation of Liquid Crystal Cell

Reference Example 19

A liquid crystal display panel was taken out of an IPS mode liquidcrystal cell-containing liquid crystal display (a 32-inch-V wide liquidcrystal television “FACE (trade name) model No. 32LC100,” 697 mm×392 mmin screen size manufactured by Toshiba Corporation). All the opticalfilms placed on both sides of the liquid crystal cell were removed fromthe liquid crystal display panel, and the glass faces (front and rear)of the liquid crystal cell were cleaned. The resulting liquid crystalcell was named Liquid Crystal Cell A.

Preparation of Laminated Film

Example 1

Pressure-Sensitive Adhesive Layer A was formed on one side ofRetardation Film A (obtained in Reference Example 1) by the same methodas in Reference Example 16. Pressure-Sensitive Adhesive Layer C wasformed on one side of Polarizing Plate A (obtained in Reference Example14) by the same method as in Reference Example 18. The release liner wasseparated from Pressure-Sensitive Adhesive Layer C on Polarizing PlateA, then, with a laminator, Polarizing Plate A was bonded to the side ofRetardation Film A, which was opposite to the side wherePressure-Sensitive Adhesive Layer A was provided. In this process, thelaminate was formed such that the direction of the slow axis ofRetardation Film A was substantially orthogonal to the direction of theabsorption axis of Polarizing Plate A. Laminated Film A prepared asdescribed above includes Polarizing Plate A, Pressure-Sensitive AdhesiveLayer C (the second pressure-sensitive adhesive layer), Retardation FilmA, and Pressure-Sensitive Adhesive Layer A (the first pressure-sensitiveadhesive layer), which are placed in this order.

Example 2

Pressure-Sensitive Adhesive Layer A was formed on one side ofRetardation Film E (obtained in Reference Example 5) by the same methodas in Reference Example 16. Pressure-Sensitive Adhesive Layer C wasformed on one side of Polarizing Plate B (obtained in Reference Example15) by the same method as in Reference Example 18. The release liner wasseparated from Polarizing Plate B provided with Pressure-SensitiveAdhesive Layer C, and Polarizing Plate B was bonded with a laminator tothe side of Retardation Film E, which was opposite to the side wherePressure-Sensitive Adhesive Layer A was provided. In this process, thelaminate was formed such that the direction of the slow axis ofRetardation Film E was substantially orthogonal to the direction of theabsorption axis of Polarizing Plate B. Laminated Film B prepared asdescribed above includes Polarizing Plate B, Pressure-Sensitive AdhesiveLayer C (the second pressure-sensitive adhesive layer), Retardation FilmE, and Pressure-Sensitive Adhesive Layer A (the first pressure-sensitiveadhesive layer), which are placed in this order.

Comparative Example 1

Pressure-Sensitive Adhesive Layer A was formed on one side ofRetardation Film M (obtained in Reference Example 13) by the same methodas in Reference Example 16. Pressure-Sensitive Adhesive Layer C wasformed on one side of Polarizing Plate A (obtained in Reference Example14) by the same method as in Reference Example 18. The release liner wasseparated from Polarizing Plate A provided with Pressure-SensitiveAdhesive Layer C, and Polarizing Plate A was bonded with a laminator tothe side of Retardation Film M, which was opposite to the side wherePressure-Sensitive Adhesive Layer A was provided. In this process, thelaminate was formed such that the direction of the slow axis ofRetardation Film M was substantially orthogonal to the direction of theabsorption axis of Polarizing Plate A. Laminated Film X prepared asdescribed above includes Polarizing Plate A, Pressure-Sensitive AdhesiveLayer C (the second pressure-sensitive adhesive layer), Retardation FilmM, and Pressure-Sensitive Adhesive Layer A (the first pressure-sensitiveadhesive layer), which are placed in this order.

Comparative Example 2

Pressure-Sensitive Adhesive Layer C was formed on one side ofRetardation Film A (obtained in Reference Example 1) by the same methodas in Reference Example 18. Pressure-Sensitive Adhesive Layer C wasformed on one side of Polarizing Plate A (obtained in Reference Example14) by the same method as in Reference Example 18. The release liner wasseparated from Polarizing Plate A provided with Pressure-SensitiveAdhesive Layer C, and Polarizing Plate A was bonded with a laminator tothe side of Retardation Film A, which was opposite to the side wherePressure-Sensitive Adhesive Layer C was provided. In this process, thelaminate was formed such that the direction of the slow axis ofRetardation Film A was substantially orthogonal to the direction of theabsorption axis of Polarizing Plate A. Laminated Film Y prepared asdescribed above includes Polarizing Plate A, Pressure-Sensitive AdhesiveLayer C (the second pressure-sensitive adhesive layer), Retardation FilmA, and Pressure-Sensitive Adhesive Layer C (the first pressure-sensitiveadhesive layer), which are placed in this order.

Evaluation of the Optical Properties of Liquid Crystal Display

Example 3

Laminated Film A (obtained in Example 1) was bonded to the viewer sideof the liquid crystal cell obtained in Reference Example 19 withPressure-Sensitive Adhesive Layer A interposed therebetween such thatthe direction of the absorption axis of Polarizing Plate A wassubstantially parallel to the direction of the long side of LiquidCrystal Cell A. Polarizing Plate A′ obtained by the process of ReferenceExample 14 was subsequently bonded to the backlight side of LiquidCrystal Cell A with Pressure-Sensitive Adhesive Layer A interposedtherebetween such that the direction of the absorption axis ofPolarizing Plate A′ was substantially orthogonal to the direction of thelong side of Liquid Crystal Cell A. Liquid crystal display panel A wascombined with a backlight unit (“LIGHT-BOX 35H (trade name) forprofessional use” manufactured by ARGO Corporation) to form a liquidcrystal display (named Liquid crystal display A). After the backlightwas turned on and allowed to run for 30 minutes, the amount of colorshift (Δa*b*) in an oblique direction and the amount of leakage of light(Y value) in an oblique direction were measured with respect to Liquidcrystal display A. Its characteristics are shown in Table 5. FIG. 10 isa graph showing Y values at a polar angle of 60° along azimuth angles of0° to 360° with respect to the liquid crystal displays of Example 3 andComparative Example 3 described later. FIG. 11 is a graph showing Δa*b*values at a polar angle of 60° along azimuth angles of 0° to 360° withrespect to the liquid crystal displays of Example 3 and ComparativeExample 3 described later.

After the backlight was allowed to run for 3 hours, the uniformity ofthe display screen of Liquid crystal display A was observed. As aresult, optical unevenness was not observed, and the whole surface ofthe panel had a high level of display uniformity (in table 5, suchdisplay uniformity is expressed by “o”). While Laminated Film A was usedin this example, the same high level of display characteristics anddisplay uniformity can be achieved using Laminated Film B of Example 2.

Comparative Example 3

A liquid crystal display panel (named Liquid crystal display Panel X)and a liquid crystal display (named Liquid crystal display X) wereprepared using the process of Example 4, except that Laminated Film Xwas used in place of Laminated Film A. After the backlight was turned onand allowed to run for 30 minutes, the amount of color shift (Δa*b*) inan oblique direction and the amount of leakage of light (Y value) in anoblique direction were measured with respect to Liquid crystal displayA. Its characteristics are shown in Table 5. After the backlight wasallowed to run for 3 hours, the uniformity of the screen of Liquidcrystal display X was observed. As a result, optical unevenness wasobserved on Liquid crystal display X (in Table 5, the result isexpressed by “x” with respect to display uniformity).

TABLE 5 Second Liquid crystal display Pressure- Pressure- Color Shift inLight Leakage in sensitive Sensitive Oblique Direction Oblique DirectionLaminated Polarizing Adhesive Retardation Adhesive (Δa*b*) (Y) DisplayFilm Plate Layer Film Layer Maximum Average Maximum Average UniformityExample 3 A A C A A 3.11 1.27 0.28 0.14 ∘ Comparative X A C M A 10.54.28 0.53 0.31 x Example 3Evaluation of Easy Peelability and Durability

Example 4

Laminated Film B (obtained in Example 2) was attached to the surface ofa non-alkali glass plate (“1737” (trade name) manufactured by CorningIncorporated) with Pressure-Sensitive Adhesive Layer A interposedtherebetween by means of a laminator. The resulting laminate wassubsequently autoclaved under a pressure of 5 atm at 50° C. for 15minutes in order to tightly bond Pressure-Sensitive Adhesive Layer A tothe non-alkali glass plate. After a lapse of one hour, Laminated Film Bwas separated by hand from the resulting sample. As a result, LaminatedFilm B was peeled by a small force (in Table 6, such easy peelability isexpressed by “o”). In addition, neither pressure-sensitive adhesivelayer nor retardation film was left on the surface of the glass plate.FIG. 12 is a photograph of the surface of the glass plate after theseparation of the laminated film of Example 3. The result of the peelingtest is shown in Table 6 together with the results of the adhesive forceand the anchoring force of each layer of Laminated Film B. While thenon-alkali glass plate was used as a substitute for a liquid crystalcell in this example, the same results can be obtained using a liquidcrystal cell in place of the non-alkali glass plate.

Another sample was prepared by the same method and allowed to stand in athermostatic chamber at 80° C. and 90% RH for 500 hours. The sample wasthen taken out of the chamber and observed. As a result, the sample hadno occurrence of peeling or bubbles (in Table 6, the result is expressedby “o” with respect to occurrence of peeling or bubbles).

Comparative Example 4

Laminated Film Y (obtained in Comparative Example 2) was attached to thesurface of a non-alkali glass plate (“1737” (trade name) manufactured byCorning Incorporated) with Pressure-Sensitive Adhesive Layer Cinterposed therebetween by means of a laminator. The resulting laminatewas subsequently autoclaved under a pressure of 5 atm at 50° C. for 15minutes in order to tightly bond Pressure-Sensitive Adhesive Layer C tothe non-alkali glass plate. After a lapse of one hour, an attempt wasmade to separate Laminated Film Y by hand from the resulting sample. Asa result, it was impossible to peel Laminated Film Y by a small force(in Table 6, the result is expressed by “x” with respect to easypeelability). Another attempt was made to separate the laminated film bya large force. As a result, peeling occurred at the interface betweenthe polarizing plate and the retardation film in the laminated film, andthe pressure-sensitive adhesive layer and the retardation film were lefton the surface of the glass plate. FIG. 13 is a photograph of thesurface of the glass plate after the separation of the laminated film ofComparative Example 4.

TABLE 6 Comparative Example Example 4 4 Laminated Film B Y FirstAdhesive Force to Glass Plate (N/25 mm) 6.0 10.2 Pressure- (F_(1A))Sensitive Anchoring Force to (N/25 mm) 22.0 25.2 Adhesive RetardationFilm (F_(1B)) Layer Second Adhesive Force to (N/25 mm) 12.5 12.5Pressure- Retardation Film (F_(2A)) Sensitive Anchoring Force toPolarizing (N/25 mm) 20.0 20.0 Adhesive Plate (F_(2B)) Layer F_(1B) −F_(1A) (N/25 mm) 160. 15.0 F_(2A) − F_(1A) (N/25 mm) 6.5 2.3 F_(2B) −F_(1A) (N/25 mm) 14.0 4.8 Easy Peelabilily ∘ x Occurrence of Peeling orBubbles ∘ (80° C. and 90% RH for 500 Hours)Evaluations

As is also clear from FIGS. 10 and 11, the liquid crystal displayincluding the laminated film of Example 1 had a high level of displaycharacteristics with very low level of light leakage and color shift inoblique directions. Also in the liquid crystal display,distortion-included optical unevenness was not observed, and gooddisplay uniformity was exhibited. In contrast, the amounts of lightleakage and color shift in an oblique direction were both relativelylarge in the liquid crystal display including the laminated film ofComparative Example 1, and optical unevenness was also observed in theliquid crystal display.

The laminated film of Example 2 did not cause peeling or bubbles withrespect to the non-alkali glass plate even in a high-temperature,high-humidity environment and exhibited a high level of adhesiveproperties and easy peelability. In contrast, the laminated film ofComparative Example 2 was not easily separable from the non-alkali glassplate, and the pressure-sensitive adhesive layer and the retardationfilm were left on the surface of the glass plate after the separationprocess.

INDUSTRIAL APPLICABILITY

From the foregoing, it will be seen that the laminated film of theinvention is very useful for improving the display characteristics andproductivity of liquid crystal displays. The liquid crystal displayincluding the laminated film according to the invention is suitable foruse in liquid crystal televisions.

1. A laminated film, comprising a polarizing plate, a retardation film,and a first pressure-sensitive adhesive layer provided in this order,the polarizing plate comprising a polarizer, a first protective layerplaced on a side of the polarizer where the retardation film isprovided, and a second protective layer placed on another side of thepolarizer which is opposite to the side where the retardation film isprovided, the retardation film being a stretched film comprising anorbornene resin, the first pressure-sensitive adhesive layer comprisinga pressure-sensitive adhesive that may be produced by crosslinking acomposition comprising a (meth)acrylate (co)polymer and a crosslinkingagent comprising a peroxide as a main component, and wherein theretardation film has an in-plane retardation (Re[590]) of 80 nm to 350nm that is measured at 23° C. and a light wavelength of 590 nm.
 2. Thelaminated film according to claim 1, wherein the first protective layerand/or the second protective layer is a polymer film comprising acellulose resin.
 3. The laminated film according to claim 1, wherein thefirst protective layer is substantially optically isotropic.
 4. Thelaminated film according to claim 1, wherein the first protective layerhas a refractive index ellipsoid satisfying the relation nx≈nz>ny,wherein nx is a refractive index in a slow axis direction, ny is arefractive index in a fast axis direction, and nz is a refractive indexin a thickness direction.
 5. The laminated film according to claim 1,wherein the retardation film has a refractive index ellipsoid satisfyingthe relation nx≧nz>ny, wherein nx is a refractive index in a slow axisdirection, ny is a refractive index in a fast axis direction, and nz isa refractive index in a thickness direction.
 6. The laminated filmaccording to claim 1, wherein the retardation film has an Nz coefficientof 0.1 to 0.7, wherein the Nz coefficient is calculated from theformula: Rth[590]/Re[590], wherein Re[590] is an in-plane retardationmeasured at 23° C. and a light wavelength of 590 nm, and Rth[590] is aretardation in a thickness direction that is measured at 23° C. and alight wavelength of 590 nm.
 7. The laminated film according to claim 1,wherein the retardation film has an absolute value of photoelasticcoefficient of 1×10⁻¹² to 10×10⁻¹² that is measured at 23° C. and alight wavelength of 590 nm.
 8. The laminated film according to claim 1,wherein the first pressure-sensitive adhesive layer has an adhesiveforce (F_(A)) of 2 N/25 mm to 10 N/25 mm at 23° C. to a glass plate,wherein the adhesive force is measured by a process that comprisespressing the laminated film with a width of 25 mm against a glass plateby one reciprocation of a 2 kg roller to bond the laminate to the glassplate, aging the laminate at 23° C. for one hour, and then measuring anadhesive strength when the laminated film is peeled in a 90-degreedirection at a rate of 300 mm/minute, wherein the adhesive strength isdetermined as the adhesive force.
 9. The laminated film according toclaim 1, wherein the first pressure-sensitive adhesive layer has ananchoring force (F_(B)) of 10 N/25 mm to 40 N/25 mm at 23° C. to theretardation film, wherein the anchoring force is measured by a processthat comprises pressing a laminate of the pressure-sensitive adhesivelayer and the retardation film each with a width of 25 mm against asurface of an indium tin oxide vapor-deposited onto a polyethyleneterephthalate film by one reciprocation of a 2 kg roller to bond thelaminate to the polyethylene terephthalate film, aging the laminate at23° C. for one hour, and then measuring an adhesive strength when thepolyethylene terephthalate film is peeled together with thepressure-sensitive adhesive layer in a 180-degree direction at a rate of300 mm/minute, wherein the adhesive strength is determined as theanchoring force.
 10. The laminated film according to claim 1, whereinthere is a difference (F_(B)−F_(A)) of at least 5 N/25 mm between theanchoring force (F_(B)) of the first pressure-sensitive adhesive layerat 23° C. to the retardation film and the adhesive force (F_(A)) of thefirst pressure-sensitive adhesive layer at 23° C. to a glass plate,wherein the anchoring force is measured by a process that comprisespressing a laminate of the pressure-sensitive adhesive layer and theretardation film each with a width of 25 mm against a surface of anindium tin oxide vapor-deposited onto a polyethylene terephthalate filmby one reciprocation of a 2 kg roller to bond the laminate to thepolyethylene terephthalate film, aging the laminate at 23° C. for onehour, and then measuring an adhesive strength when the polyethyleneterephthalate film is peeled together with the pressure-sensitiveadhesive layer in a 180-degree direction at a rate of 300 mm/minute,wherein the adhesive strength is determined as the anchoring force, andthe adhesive force is measured by a process that comprises pressing thelaminated film with a width of 25 mm against a glass plate by onereciprocation of a 2 kg roller to bond the laminate to the glass plate,aging the laminate at 23° C. for one hour, and then measuring anadhesive strength when the laminated film is peeled in a 90-degreedirection at a rate of 300 mm/minute, wherein the adhesive strength isdetermined as the adhesive force.
 11. The laminated film according toclaim 1, wherein the (meth)acrylate (co)polymer is a copolymer of a(meth)acrylate monomer having a straight or branched alkyl group of 1 to8 carbon atoms and another (meth)acrylate monomer having a straight orbranched alkyl group of 1 to 8 carbon atoms in which at least onehydrogen atom is replaced with a hydroxyl group.
 12. The laminated filmaccording to claim 1, wherein the crosslinking agent comprising theperoxide as a main component has a content of 0.01 to 1.0 part byweight, based on 100 parts by weight of the (meth)acrylate (co)polymer.13. The laminated film according to claim 1, wherein the firstpressure-sensitive adhesive layer comprises a pressure-sensitiveadhesive that may be produced by crosslinking a composition comprising a(meth)acrylate (co)polymer, an isocyanate group-containing compound, asilane coupling agent, and a crosslinking agent comprising a peroxide asa main component, the isocyanate group-containing compound has a contentof 0.005 to 1.0 part by weight, based on 100 parts by weight of the(meth)acrylate (co)polymer, and the silane coupling agent has a contentof 0.001 to 2.0 parts by weight, based on 100 parts by weight of the(meth)acrylate (co)polymer.
 14. The laminated film according to claim 1,wherein the pressure-sensitive adhesive has a glass transitiontemperature (Tg) of −70° C. to −10° C.
 15. The laminated film accordingto claim 1, wherein the pressure-sensitive adhesive has a moisturecontent of 1.0% or less.
 16. The laminated film according to claim 1,further comprising a second pressure-sensitive adhesive layer betweenthe polarizing plate and the retardation film, wherein the secondpressure-sensitive adhesive layer comprises a pressure-sensitiveadhesive that may be produced by crosslinking a composition comprising a(meth)acrylate (co)polymer, a silane coupling agent, and a crosslinkingagent comprising an isocyanate group-containing compound as a maincomponent.
 17. A liquid crystal display panel, comprising the laminatedfilm according to claim 1, and a liquid crystal cell.
 18. A liquidcrystal display, comprising the liquid crystal panel according to claim17.